diff --git a/include/psa/crypto.h b/include/psa/crypto.h
index 93f8968..25c3cb4 100644
--- a/include/psa/crypto.h
+++ b/include/psa/crypto.h
@@ -193,7 +193,7 @@
  *         the policy has been saved to persistent storage. Implementations
  *         may defer saving the policy until the key material is created.
  * \retval #PSA_ERROR_INVALID_HANDLE
- * \retval #PSA_ERROR_OCCUPIED_SLOT
+ * \retval #PSA_ERROR_ALREADY_EXISTS
  * \retval #PSA_ERROR_NOT_SUPPORTED
  * \retval #PSA_ERROR_INVALID_ARGUMENT
  * \retval #PSA_ERROR_COMMUNICATION_FAILURE
@@ -285,7 +285,7 @@
  *         Success. The application can now use the value of `*handle`
  *         to access the newly allocated key slot.
  * \retval #PSA_ERROR_INSUFFICIENT_MEMORY
- * \retval #PSA_ERROR_EMPTY_SLOT
+ * \retval #PSA_ERROR_DOES_NOT_EXIST
  * \retval #PSA_ERROR_INVALID_ARGUMENT
  *         \p lifetime is invalid, for example #PSA_KEY_LIFETIME_VOLATILE.
  * \retval #PSA_ERROR_INVALID_ARGUMENT
@@ -322,7 +322,7 @@
  *         to access the newly allocated key slot.
  * \retval #PSA_ERROR_INSUFFICIENT_MEMORY
  * \retval #PSA_ERROR_INSUFFICIENT_STORAGE
- * \retval #PSA_ERROR_OCCUPIED_SLOT
+ * \retval #PSA_ERROR_ALREADY_EXISTS
  *         There is already a key with the identifier \p id in the storage
  *         area designated by \p lifetime.
  * \retval #PSA_ERROR_INVALID_ARGUMENT
@@ -401,7 +401,7 @@
  * \retval #PSA_ERROR_INVALID_ARGUMENT
  *         The key slot is invalid,
  *         or the key data is not correctly formatted.
- * \retval #PSA_ERROR_OCCUPIED_SLOT
+ * \retval #PSA_ERROR_ALREADY_EXISTS
  *         There is already a key in the specified slot.
  * \retval #PSA_ERROR_INSUFFICIENT_MEMORY
  * \retval #PSA_ERROR_INSUFFICIENT_STORAGE
@@ -470,7 +470,7 @@
  *
  * \retval #PSA_SUCCESS
  * \retval #PSA_ERROR_INVALID_HANDLE
- * \retval #PSA_ERROR_EMPTY_SLOT
+ * \retval #PSA_ERROR_DOES_NOT_EXIST
  *         The handle is to a key slot which does not contain key material yet.
  * \retval #PSA_ERROR_COMMUNICATION_FAILURE
  * \retval #PSA_ERROR_HARDWARE_FAILURE
@@ -554,7 +554,7 @@
  *
  * \retval #PSA_SUCCESS
  * \retval #PSA_ERROR_INVALID_HANDLE
- * \retval #PSA_ERROR_EMPTY_SLOT
+ * \retval #PSA_ERROR_DOES_NOT_EXIST
  * \retval #PSA_ERROR_NOT_PERMITTED
  * \retval #PSA_ERROR_NOT_SUPPORTED
  * \retval #PSA_ERROR_BUFFER_TOO_SMALL
@@ -641,7 +641,7 @@
  *
  * \retval #PSA_SUCCESS
  * \retval #PSA_ERROR_INVALID_HANDLE
- * \retval #PSA_ERROR_EMPTY_SLOT
+ * \retval #PSA_ERROR_DOES_NOT_EXIST
  * \retval #PSA_ERROR_INVALID_ARGUMENT
  *         The key is neither a public key nor a key pair.
  * \retval #PSA_ERROR_NOT_SUPPORTED
@@ -710,9 +710,9 @@
  *
  * \retval #PSA_SUCCESS
  * \retval #PSA_ERROR_INVALID_HANDLE
- * \retval #PSA_ERROR_OCCUPIED_SLOT
+ * \retval #PSA_ERROR_ALREADY_EXISTS
  *         \p target already contains key material.
- * \retval #PSA_ERROR_EMPTY_SLOT
+ * \retval #PSA_ERROR_DOES_NOT_EXIST
  *         \p source does not contain key material.
  * \retval #PSA_ERROR_INVALID_ARGUMENT
  *         The policy constraints on the source, on the target and
@@ -1071,7 +1071,7 @@
  * \retval #PSA_SUCCESS
  *         Success.
  * \retval #PSA_ERROR_INVALID_HANDLE
- * \retval #PSA_ERROR_EMPTY_SLOT
+ * \retval #PSA_ERROR_DOES_NOT_EXIST
  * \retval #PSA_ERROR_NOT_PERMITTED
  * \retval #PSA_ERROR_INVALID_ARGUMENT
  *         \p key is not compatible with \p alg.
@@ -1128,7 +1128,7 @@
  * \retval #PSA_SUCCESS
  *         Success.
  * \retval #PSA_ERROR_INVALID_HANDLE
- * \retval #PSA_ERROR_EMPTY_SLOT
+ * \retval #PSA_ERROR_DOES_NOT_EXIST
  * \retval #PSA_ERROR_NOT_PERMITTED
  * \retval #PSA_ERROR_INVALID_ARGUMENT
  *         \c key is not compatible with \c alg.
@@ -1373,7 +1373,7 @@
  * \retval #PSA_SUCCESS
  *         Success.
  * \retval #PSA_ERROR_INVALID_HANDLE
- * \retval #PSA_ERROR_EMPTY_SLOT
+ * \retval #PSA_ERROR_DOES_NOT_EXIST
  * \retval #PSA_ERROR_NOT_PERMITTED
  * \retval #PSA_ERROR_INVALID_ARGUMENT
  *         \p key is not compatible with \p alg.
@@ -1432,7 +1432,7 @@
  * \retval #PSA_SUCCESS
  *         Success.
  * \retval #PSA_ERROR_INVALID_HANDLE
- * \retval #PSA_ERROR_EMPTY_SLOT
+ * \retval #PSA_ERROR_DOES_NOT_EXIST
  * \retval #PSA_ERROR_NOT_PERMITTED
  * \retval #PSA_ERROR_INVALID_ARGUMENT
  *         \p key is not compatible with \p alg.
@@ -1660,7 +1660,7 @@
  * \retval #PSA_SUCCESS
  *         Success.
  * \retval #PSA_ERROR_INVALID_HANDLE
- * \retval #PSA_ERROR_EMPTY_SLOT
+ * \retval #PSA_ERROR_DOES_NOT_EXIST
  * \retval #PSA_ERROR_NOT_PERMITTED
  * \retval #PSA_ERROR_INVALID_ARGUMENT
  *         \p key is not compatible with \p alg.
@@ -1716,7 +1716,7 @@
  * \retval #PSA_SUCCESS
  *         Success.
  * \retval #PSA_ERROR_INVALID_HANDLE
- * \retval #PSA_ERROR_EMPTY_SLOT
+ * \retval #PSA_ERROR_DOES_NOT_EXIST
  * \retval #PSA_ERROR_INVALID_SIGNATURE
  *         The ciphertext is not authentic.
  * \retval #PSA_ERROR_NOT_PERMITTED
@@ -2034,7 +2034,7 @@
  * \param output_length     Number of bytes to output.
  *
  * \retval #PSA_SUCCESS
- * \retval #PSA_ERROR_INSUFFICIENT_CAPACITY
+ * \retval #PSA_ERROR_INSUFFICIENT_DATA
  *                          There were fewer than \p output_length bytes
  *                          in the generator. Note that in this case, no
  *                          output is written to the output buffer.
@@ -2076,7 +2076,7 @@
  *         Success.
  *         If the key is persistent, the key material and the key's metadata
  *         have been saved to persistent storage.
- * \retval #PSA_ERROR_INSUFFICIENT_CAPACITY
+ * \retval #PSA_ERROR_INSUFFICIENT_DATA
  *                          There were fewer than \p output_length bytes
  *                          in the generator. Note that in this case, no
  *                          output is written to the output buffer.
@@ -2088,7 +2088,7 @@
  *         implementation in general or in this particular slot.
  * \retval #PSA_ERROR_BAD_STATE
  * \retval #PSA_ERROR_INVALID_HANDLE
- * \retval #PSA_ERROR_OCCUPIED_SLOT
+ * \retval #PSA_ERROR_ALREADY_EXISTS
  *         There is already a key in the specified slot.
  * \retval #PSA_ERROR_INSUFFICIENT_MEMORY
  * \retval #PSA_ERROR_INSUFFICIENT_STORAGE
@@ -2172,7 +2172,7 @@
  * \retval #PSA_SUCCESS
  *         Success.
  * \retval #PSA_ERROR_INVALID_HANDLE
- * \retval #PSA_ERROR_EMPTY_SLOT
+ * \retval #PSA_ERROR_DOES_NOT_EXIST
  * \retval #PSA_ERROR_NOT_PERMITTED
  * \retval #PSA_ERROR_INVALID_ARGUMENT
  *         \c key is not compatible with \c alg,
@@ -2233,7 +2233,7 @@
  * \retval #PSA_SUCCESS
  *         Success.
  * \retval #PSA_ERROR_INVALID_HANDLE
- * \retval #PSA_ERROR_EMPTY_SLOT
+ * \retval #PSA_ERROR_DOES_NOT_EXIST
  * \retval #PSA_ERROR_NOT_PERMITTED
  * \retval #PSA_ERROR_INVALID_ARGUMENT
  *         \c private_key is not compatible with \c alg,
@@ -2332,7 +2332,7 @@
  *         If the key is persistent, the key material and the key's metadata
  *         have been saved to persistent storage.
  * \retval #PSA_ERROR_INVALID_HANDLE
- * \retval #PSA_ERROR_OCCUPIED_SLOT
+ * \retval #PSA_ERROR_ALREADY_EXISTS
  *         There is already a key in the specified slot.
  * \retval #PSA_ERROR_NOT_SUPPORTED
  * \retval #PSA_ERROR_INVALID_ARGUMENT
diff --git a/include/psa/crypto_se_driver.h b/include/psa/crypto_se_driver.h
index 0578664..20cd4b4 100644
--- a/include/psa/crypto_se_driver.h
+++ b/include/psa/crypto_se_driver.h
@@ -754,7 +754,7 @@
  *                              that make up the key data.
  *
  * \retval #PSA_SUCCESS
- * \retval #PSA_ERROR_EMPTY_SLOT
+ * \retval #PSA_ERROR_DOES_NOT_EXIST
  * \retval #PSA_ERROR_NOT_PERMITTED
  * \retval #PSA_ERROR_NOT_SUPPORTED
  * \retval #PSA_ERROR_COMMUNICATION_FAILURE
diff --git a/include/psa/crypto_types.h b/include/psa/crypto_types.h
index 9b44d6a..29c9853 100644
--- a/include/psa/crypto_types.h
+++ b/include/psa/crypto_types.h
@@ -47,8 +47,13 @@
  * This is either #PSA_SUCCESS (which is zero), indicating success,
  * or a nonzero value indicating that an error occurred. Errors are
  * encoded as one of the \c PSA_ERROR_xxx values defined here.
+ * If #PSA_SUCCESS is already defined, it means that #psa_status_t
+ * is also defined in an external header, so prevent its multiple
+ * definition.
  */
+#ifndef PSA_SUCCESS
 typedef int32_t psa_status_t;
+#endif
 
 /**@}*/
 
diff --git a/include/psa/crypto_values.h b/include/psa/crypto_values.h
index 2ae72e0..d42d8c2 100644
--- a/include/psa/crypto_values.h
+++ b/include/psa/crypto_values.h
@@ -40,25 +40,17 @@
  * @{
  */
 
-#if !defined(PSA_SUCCESS)
-/* If PSA_SUCCESS is defined, assume that PSA crypto is being used
- * together with PSA IPC, which also defines the identifier
- * PSA_SUCCESS. We must not define PSA_SUCCESS ourselves in that case;
- * the other error code names don't clash. This is a temporary hack
- * until we unify error reporting in PSA IPC and PSA crypto.
- *
- * Note that psa_defs.h must be included before this header!
- */
+/* PSA error codes */
+
 /** The action was completed successfully. */
 #define PSA_SUCCESS ((psa_status_t)0)
-#endif /* !defined(PSA_SUCCESS) */
 
 /** An error occurred that does not correspond to any defined
  * failure cause.
  *
  * Implementations may use this error code if none of the other standard
  * error codes are applicable. */
-#define PSA_ERROR_UNKNOWN_ERROR         ((psa_status_t)1)
+#define PSA_ERROR_GENERIC_ERROR         ((psa_status_t)-132)
 
 /** The requested operation or a parameter is not supported
  * by this implementation.
@@ -67,7 +59,7 @@
  * parameter such as a key type, algorithm, etc. is not recognized.
  * If a combination of parameters is recognized and identified as
  * not valid, return #PSA_ERROR_INVALID_ARGUMENT instead. */
-#define PSA_ERROR_NOT_SUPPORTED         ((psa_status_t)2)
+#define PSA_ERROR_NOT_SUPPORTED         ((psa_status_t)-134)
 
 /** The requested action is denied by a policy.
  *
@@ -80,7 +72,7 @@
  * not valid or not supported, it is unspecified whether the function
  * returns #PSA_ERROR_NOT_PERMITTED, #PSA_ERROR_NOT_SUPPORTED or
  * #PSA_ERROR_INVALID_ARGUMENT. */
-#define PSA_ERROR_NOT_PERMITTED         ((psa_status_t)3)
+#define PSA_ERROR_NOT_PERMITTED         ((psa_status_t)-133)
 
 /** An output buffer is too small.
  *
@@ -92,23 +84,19 @@
  * buffer would succeed. However implementations may return this
  * error if a function has invalid or unsupported parameters in addition
  * to the parameters that determine the necessary output buffer size. */
-#define PSA_ERROR_BUFFER_TOO_SMALL      ((psa_status_t)4)
+#define PSA_ERROR_BUFFER_TOO_SMALL      ((psa_status_t)-138)
 
-/** A slot is occupied, but must be empty to carry out the
- * requested action.
+/** Asking for an item that already exists
  *
- * If a handle is invalid, it does not designate an occupied slot.
- * The error for an invalid handle is #PSA_ERROR_INVALID_HANDLE.
- */
-#define PSA_ERROR_OCCUPIED_SLOT         ((psa_status_t)5)
+ * Implementations should return this error, when attempting
+ * to write an item (like a key) that already exists. */
+#define PSA_ERROR_ALREADY_EXISTS        ((psa_status_t)-139)
 
-/** A slot is empty, but must be occupied to carry out the
- * requested action.
+/** Asking for an item that doesn't exist
  *
- * If a handle is invalid, it does not designate an empty slot.
- * The error for an invalid handle is #PSA_ERROR_INVALID_HANDLE.
- */
-#define PSA_ERROR_EMPTY_SLOT            ((psa_status_t)6)
+ * Implementations should return this error, if a requested item (like
+ * a key) does not exist. */
+#define PSA_ERROR_DOES_NOT_EXIST        ((psa_status_t)-140)
 
 /** The requested action cannot be performed in the current state.
  *
@@ -118,9 +106,9 @@
  *
  * Implementations shall not return this error code to indicate
  * that a key slot is occupied when it needs to be free or vice versa,
- * but shall return #PSA_ERROR_OCCUPIED_SLOT or #PSA_ERROR_EMPTY_SLOT
+ * but shall return #PSA_ERROR_ALREADY_EXISTS or #PSA_ERROR_DOES_NOT_EXIST
  * as applicable. */
-#define PSA_ERROR_BAD_STATE             ((psa_status_t)7)
+#define PSA_ERROR_BAD_STATE             ((psa_status_t)-137)
 
 /** The parameters passed to the function are invalid.
  *
@@ -129,20 +117,20 @@
  *
  * Implementations shall not return this error code to indicate
  * that a key slot is occupied when it needs to be free or vice versa,
- * but shall return #PSA_ERROR_OCCUPIED_SLOT or #PSA_ERROR_EMPTY_SLOT
+ * but shall return #PSA_ERROR_ALREADY_EXISTS or #PSA_ERROR_DOES_NOT_EXIST
  * as applicable.
  *
  * Implementation shall not return this error code to indicate that a
  * key handle is invalid, but shall return #PSA_ERROR_INVALID_HANDLE
  * instead.
  */
-#define PSA_ERROR_INVALID_ARGUMENT      ((psa_status_t)8)
+#define PSA_ERROR_INVALID_ARGUMENT      ((psa_status_t)-135)
 
 /** There is not enough runtime memory.
  *
  * If the action is carried out across multiple security realms, this
  * error can refer to available memory in any of the security realms. */
-#define PSA_ERROR_INSUFFICIENT_MEMORY   ((psa_status_t)9)
+#define PSA_ERROR_INSUFFICIENT_MEMORY   ((psa_status_t)-141)
 
 /** There is not enough persistent storage.
  *
@@ -151,7 +139,7 @@
  * many functions that do not otherwise access storage may return this
  * error code if the implementation requires a mandatory log entry for
  * the requested action and the log storage space is full. */
-#define PSA_ERROR_INSUFFICIENT_STORAGE  ((psa_status_t)10)
+#define PSA_ERROR_INSUFFICIENT_STORAGE  ((psa_status_t)-142)
 
 /** There was a communication failure inside the implementation.
  *
@@ -168,7 +156,7 @@
  * cryptoprocessor but there was a breakdown of communication before
  * the cryptoprocessor could report the status to the application.
  */
-#define PSA_ERROR_COMMUNICATION_FAILURE ((psa_status_t)11)
+#define PSA_ERROR_COMMUNICATION_FAILURE ((psa_status_t)-145)
 
 /** There was a storage failure that may have led to data loss.
  *
@@ -193,13 +181,13 @@
  * permanent storage corruption. However application writers should
  * keep in mind that transient errors while reading the storage may be
  * reported using this error code. */
-#define PSA_ERROR_STORAGE_FAILURE       ((psa_status_t)12)
+#define PSA_ERROR_STORAGE_FAILURE       ((psa_status_t)-146)
 
 /** A hardware failure was detected.
  *
  * A hardware failure may be transient or permanent depending on the
  * cause. */
-#define PSA_ERROR_HARDWARE_FAILURE      ((psa_status_t)13)
+#define PSA_ERROR_HARDWARE_FAILURE      ((psa_status_t)-147)
 
 /** A tampering attempt was detected.
  *
@@ -230,7 +218,7 @@
  * This error indicates an attack against the application. Implementations
  * shall not return this error code as a consequence of the behavior of
  * the application itself. */
-#define PSA_ERROR_TAMPERING_DETECTED    ((psa_status_t)14)
+#define PSA_ERROR_TAMPERING_DETECTED    ((psa_status_t)-151)
 
 /** There is not enough entropy to generate random data needed
  * for the requested action.
@@ -249,7 +237,7 @@
  * secure pseudorandom generator (PRNG). However implementations may return
  * this error at any time if a policy requires the PRNG to be reseeded
  * during normal operation. */
-#define PSA_ERROR_INSUFFICIENT_ENTROPY  ((psa_status_t)15)
+#define PSA_ERROR_INSUFFICIENT_ENTROPY  ((psa_status_t)-148)
 
 /** The signature, MAC or hash is incorrect.
  *
@@ -259,7 +247,7 @@
  *
  * If the value to verify has an invalid size, implementations may return
  * either #PSA_ERROR_INVALID_ARGUMENT or #PSA_ERROR_INVALID_SIGNATURE. */
-#define PSA_ERROR_INVALID_SIGNATURE     ((psa_status_t)16)
+#define PSA_ERROR_INVALID_SIGNATURE     ((psa_status_t)-149)
 
 /** The decrypted padding is incorrect.
  *
@@ -275,17 +263,15 @@
  * as close as possible to indistinguishable to an external observer.
  * In particular, the timing of a decryption operation should not
  * depend on the validity of the padding. */
-#define PSA_ERROR_INVALID_PADDING       ((psa_status_t)17)
+#define PSA_ERROR_INVALID_PADDING       ((psa_status_t)-150)
 
-/** The generator has insufficient capacity left.
- *
- * Once a function returns this error, attempts to read from the
- * generator will always return this error. */
-#define PSA_ERROR_INSUFFICIENT_CAPACITY ((psa_status_t)18)
+/** Return this error when there's insufficient data when attempting
+ * to read from a resource. */
+#define PSA_ERROR_INSUFFICIENT_DATA     ((psa_status_t)-143)
 
 /** The key handle is not valid.
  */
-#define PSA_ERROR_INVALID_HANDLE        ((psa_status_t)19)
+#define PSA_ERROR_INVALID_HANDLE        ((psa_status_t)-136)
 
 /**@}*/
 
diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index 5bf4f99..fd9f387 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -346,7 +346,7 @@
             return( PSA_ERROR_HARDWARE_FAILURE );
 
         default:
-            return( PSA_ERROR_UNKNOWN_ERROR );
+            return( PSA_ERROR_GENERIC_ERROR );
     }
 }
 
@@ -742,7 +742,7 @@
         return( status );
 
     if( slot->type != PSA_KEY_TYPE_NONE )
-        return( PSA_ERROR_OCCUPIED_SLOT );
+        return( PSA_ERROR_ALREADY_EXISTS );
 
     *p_slot = slot;
     return( status );
@@ -839,7 +839,7 @@
     if( status != PSA_SUCCESS )
         return( status );
     if( slot->type == PSA_KEY_TYPE_NONE )
-        return( PSA_ERROR_EMPTY_SLOT );
+        return( PSA_ERROR_DOES_NOT_EXIST );
 
     /* Enforce that usage policy for the key slot contains all the flags
      * required by the usage parameter. There is one exception: public
@@ -1001,7 +1001,7 @@
         return( status );
 
     if( slot->type == PSA_KEY_TYPE_NONE )
-        return( PSA_ERROR_EMPTY_SLOT );
+        return( PSA_ERROR_DOES_NOT_EXIST );
     if( type != NULL )
         *type = slot->type;
     if( bits != NULL )
@@ -3098,7 +3098,7 @@
                                 size_t output_size,
                                 size_t *output_length )
 {
-    psa_status_t status = PSA_ERROR_UNKNOWN_ERROR;
+    psa_status_t status = PSA_ERROR_GENERIC_ERROR;
     int cipher_ret = MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE;
     uint8_t temp_output_buffer[MBEDTLS_MAX_BLOCK_LENGTH];
 
@@ -3855,7 +3855,7 @@
         generator->capacity = 0;
         /* Go through the error path to wipe all confidential data now
          * that the generator object is useless. */
-        status = PSA_ERROR_INSUFFICIENT_CAPACITY;
+        status = PSA_ERROR_INSUFFICIENT_DATA;
         goto exit;
     }
     if( output_length == 0 &&
@@ -3867,7 +3867,7 @@
          * INSUFFICIENT_CAPACITY, which is right for a finished
          * generator, for consistency with the case when
          * output_length > 0. */
-        return( PSA_ERROR_INSUFFICIENT_CAPACITY );
+        return( PSA_ERROR_INSUFFICIENT_DATA );
     }
     generator->capacity -= output_length;
 
@@ -4400,7 +4400,7 @@
             return( PSA_SUCCESS );
 
         case PSA_ITS_ERROR_UID_NOT_FOUND:
-            return( PSA_ERROR_EMPTY_SLOT );
+            return( PSA_ERROR_DOES_NOT_EXIST );
 
         case PSA_ITS_ERROR_STORAGE_FAILURE:
             return( PSA_ERROR_STORAGE_FAILURE );
@@ -4417,10 +4417,10 @@
             return( PSA_ERROR_NOT_SUPPORTED );
 
         case PSA_ITS_ERROR_WRITE_ONCE:
-            return( PSA_ERROR_OCCUPIED_SLOT );
+            return( PSA_ERROR_ALREADY_EXISTS );
 
         default:
-            return( PSA_ERROR_UNKNOWN_ERROR );
+            return( PSA_ERROR_GENERIC_ERROR );
     }
 }
 
diff --git a/library/psa_crypto_slot_management.c b/library/psa_crypto_slot_management.c
index c151c5e..dad23c4 100644
--- a/library/psa_crypto_slot_management.c
+++ b/library/psa_crypto_slot_management.c
@@ -194,7 +194,7 @@
  *
  * \retval #PSA_SUCCESS
  *         The slot content was loaded successfully.
- * \retval #PSA_ERROR_EMPTY_SLOT
+ * \retval #PSA_ERROR_DOES_NOT_EXIST
  *         There is no content for this slot in persistent storage.
  * \retval #PSA_ERROR_INVALID_HANDLE
  * \retval #PSA_ERROR_INVALID_ARGUMENT
@@ -274,11 +274,11 @@
     psa_status_t status;
 
     status = persistent_key_setup( lifetime, id, handle,
-                                   PSA_ERROR_EMPTY_SLOT );
+                                   PSA_ERROR_DOES_NOT_EXIST );
     switch( status )
     {
-        case PSA_SUCCESS: return( PSA_ERROR_OCCUPIED_SLOT );
-        case PSA_ERROR_EMPTY_SLOT: return( PSA_SUCCESS );
+        case PSA_SUCCESS: return( PSA_ERROR_ALREADY_EXISTS );
+        case PSA_ERROR_DOES_NOT_EXIST: return( PSA_SUCCESS );
         default: return( status );
     }
 }
diff --git a/library/psa_crypto_storage.h b/library/psa_crypto_storage.h
index 85881c1..9da009d 100644
--- a/library/psa_crypto_storage.h
+++ b/library/psa_crypto_storage.h
@@ -84,7 +84,7 @@
  * \retval PSA_ERROR_INSUFFICIENT_MEMORY
  * \retval PSA_ERROR_INSUFFICIENT_STORAGE
  * \retval PSA_ERROR_STORAGE_FAILURE
- * \retval PSA_ERROR_OCCUPIED_SLOT
+ * \retval PSA_ERROR_ALREADY_EXISTS
  */
 psa_status_t psa_save_persistent_key( const psa_key_id_t key,
                                       const psa_key_type_t type,
@@ -115,7 +115,7 @@
  * \retval PSA_SUCCESS
  * \retval PSA_ERROR_INSUFFICIENT_MEMORY
  * \retval PSA_ERROR_STORAGE_FAILURE
- * \retval PSA_ERROR_EMPTY_SLOT
+ * \retval PSA_ERROR_DOES_NOT_EXIST
  */
 psa_status_t psa_load_persistent_key( psa_key_id_t key,
                                       psa_key_type_t *type,
diff --git a/library/psa_crypto_storage_backend.h b/library/psa_crypto_storage_backend.h
index 47896b8..83bd2f3 100644
--- a/library/psa_crypto_storage_backend.h
+++ b/library/psa_crypto_storage_backend.h
@@ -54,7 +54,7 @@
  *
  * \retval PSA_SUCCESS
  * \retval PSA_ERROR_STORAGE_FAILURE
- * \retval PSA_ERROR_EMPTY_SLOT
+ * \retval PSA_ERROR_DOES_NOT_EXIST
  */
 psa_status_t psa_crypto_storage_load( const psa_key_id_t key, uint8_t *data,
                                       size_t data_size );
@@ -73,7 +73,7 @@
  * \retval PSA_SUCCESS
  * \retval PSA_ERROR_INSUFFICIENT_STORAGE
  * \retval PSA_ERROR_STORAGE_FAILURE
- * \retval PSA_ERROR_OCCUPIED_SLOT
+ * \retval PSA_ERROR_ALREADY_EXISTS
  */
 psa_status_t psa_crypto_storage_store( const psa_key_id_t key,
                                        const uint8_t *data,
diff --git a/library/psa_crypto_storage_file.c b/library/psa_crypto_storage_file.c
index 87420be..a6e732d 100644
--- a/library/psa_crypto_storage_file.c
+++ b/library/psa_crypto_storage_file.c
@@ -118,7 +118,7 @@
     key_id_to_location( key, slot_location, MAX_LOCATION_LEN );
 
     if( psa_is_key_present_in_storage( key ) == 1 )
-        return( PSA_ERROR_OCCUPIED_SLOT );
+        return( PSA_ERROR_ALREADY_EXISTS );
 
     file = fopen( temp_location, "wb" );
     if( file == NULL )
@@ -186,7 +186,7 @@
 
     file = fopen( slot_location, "rb" );
     if( file == NULL )
-        return( PSA_ERROR_EMPTY_SLOT );
+        return( PSA_ERROR_DOES_NOT_EXIST );
 
     if( fseek( file, 0, SEEK_END ) != 0 )
     {
diff --git a/library/psa_crypto_storage_its.c b/library/psa_crypto_storage_its.c
index 1873c69..f97a5d7 100644
--- a/library/psa_crypto_storage_its.c
+++ b/library/psa_crypto_storage_its.c
@@ -27,6 +27,7 @@
 
 #if defined(MBEDTLS_PSA_CRYPTO_STORAGE_ITS_C)
 
+#include "psa/error.h"
 #include "psa/crypto.h"
 #include "psa_crypto_storage_backend.h"
 #include "psa/internal_trusted_storage.h"
@@ -43,7 +44,7 @@
             return( PSA_SUCCESS );
 
         case PSA_ITS_ERROR_UID_NOT_FOUND:
-            return( PSA_ERROR_EMPTY_SLOT );
+            return( PSA_ERROR_DOES_NOT_EXIST );
 
         case PSA_ITS_ERROR_STORAGE_FAILURE:
             return( PSA_ERROR_STORAGE_FAILURE );
@@ -60,7 +61,7 @@
             return( PSA_ERROR_NOT_SUPPORTED );
 
         case PSA_ITS_ERROR_WRITE_ONCE:
-            return( PSA_ERROR_OCCUPIED_SLOT );
+            return( PSA_ERROR_ALREADY_EXISTS );
 
         default:
             return( PSA_ERROR_UNKNOWN_ERROR );
@@ -114,7 +115,7 @@
     struct psa_its_info_t data_identifier_info;
 
     if( psa_is_key_present_in_storage( key ) == 1 )
-        return( PSA_ERROR_OCCUPIED_SLOT );
+        return( PSA_ERROR_ALREADY_EXISTS );
 
     ret = psa_its_set( data_identifier, data_length, data, 0 );
     status = its_to_psa_error( ret );
diff --git a/tests/suites/test_suite_psa_crypto.function b/tests/suites/test_suite_psa_crypto.function
index 929d1b2..92b6fb0 100644
--- a/tests/suites/test_suite_psa_crypto.function
+++ b/tests/suites/test_suite_psa_crypto.function
@@ -419,10 +419,10 @@
     size_t key_bits;
     uint8_t *public_key = NULL;
     size_t public_key_length;
-    /* Return UNKNOWN_ERROR if something other than the final call to
+    /* Return GENERIC_ERROR if something other than the final call to
      * psa_key_agreement fails. This isn't fully satisfactory, but it's
      * good enough: callers will report it as a failed test anyway. */
-    psa_status_t status = PSA_ERROR_UNKNOWN_ERROR;
+    psa_status_t status = PSA_ERROR_GENERIC_ERROR;
 
     PSA_ASSERT( psa_get_key_information( handle,
                                          &private_key_type,
@@ -1027,7 +1027,7 @@
     PSA_ASSERT( psa_set_key_policy( handle, &policy ) );
 
     TEST_EQUAL( psa_get_key_information( handle, NULL, NULL ),
-                PSA_ERROR_EMPTY_SLOT );
+                PSA_ERROR_DOES_NOT_EXIST );
 
     /* Import the key */
     PSA_ASSERT( psa_import_key( handle, type,
@@ -1114,7 +1114,7 @@
 
     /* Import the key again */
     status = psa_import_key( handle, type, data, sizeof( data ) );
-    TEST_EQUAL( status, PSA_ERROR_OCCUPIED_SLOT );
+    TEST_EQUAL( status, PSA_ERROR_ALREADY_EXISTS );
 
 exit:
     mbedtls_psa_crypto_free( );
@@ -1164,7 +1164,7 @@
     status = psa_export_key( handle,
                              exported, export_size,
                              &exported_length );
-    TEST_EQUAL( status, PSA_ERROR_EMPTY_SLOT );
+    TEST_EQUAL( status, PSA_ERROR_DOES_NOT_EXIST );
 
 exit:
     mbedtls_psa_crypto_free( );
@@ -1187,7 +1187,7 @@
     PSA_ASSERT( psa_set_key_policy( handle, &policy ) );
 
     status = psa_cipher_encrypt_setup( &operation, handle, exercise_alg );
-    TEST_EQUAL( status, PSA_ERROR_EMPTY_SLOT );
+    TEST_EQUAL( status, PSA_ERROR_DOES_NOT_EXIST );
 
 exit:
     psa_cipher_abort( &operation );
@@ -1220,7 +1220,7 @@
     status = psa_export_key( handle,
                              exported, export_size,
                              &exported_length );
-    TEST_EQUAL( status, PSA_ERROR_EMPTY_SLOT );
+    TEST_EQUAL( status, PSA_ERROR_DOES_NOT_EXIST );
 
 exit:
     mbedtls_psa_crypto_free( );
@@ -1248,7 +1248,7 @@
     TEST_EQUAL( status, expected_import_status );
 
     status = psa_cipher_encrypt_setup( &operation, handle, exercise_alg );
-    TEST_EQUAL( status, PSA_ERROR_EMPTY_SLOT );
+    TEST_EQUAL( status, PSA_ERROR_DOES_NOT_EXIST );
 
 exit:
     psa_cipher_abort( &operation );
@@ -1937,7 +1937,7 @@
     /* Test that the target slot is unaffected. */
     TEST_EQUAL( psa_get_key_information( target_handle,
                                          &target_type, &target_bits ),
-                PSA_ERROR_EMPTY_SLOT );
+                PSA_ERROR_DOES_NOT_EXIST );
     PSA_ASSERT( psa_get_key_policy( target_handle, &target_policy ) );
     TEST_EQUAL( target_usage, psa_key_policy_get_usage( &target_policy ) );
     TEST_EQUAL( target_alg, psa_key_policy_get_algorithm( &target_policy ) );
@@ -3614,7 +3614,7 @@
     PSA_ASSERT( psa_generator_read( &generator, buffer, capacity ) );
 
     TEST_EQUAL( psa_generator_read( &generator, buffer, capacity ),
-                PSA_ERROR_INSUFFICIENT_CAPACITY );
+                PSA_ERROR_INSUFFICIENT_DATA );
 
 exit:
     psa_generator_abort( &generator );
@@ -3632,7 +3632,7 @@
     psa_crypto_generator_t generator = PSA_CRYPTO_GENERATOR_INIT;
 
     TEST_ASSERT( psa_generator_read( &generator, output_buffer, buffer_size )
-                 == PSA_ERROR_INSUFFICIENT_CAPACITY ); // should be PSA_ERROR_BAD_STATE:#183
+                 == PSA_ERROR_INSUFFICIENT_DATA ); // should be PSA_ERROR_BAD_STATE:#183
 
     TEST_ASSERT( psa_get_generator_capacity( &generator, &capacity )
                  == PSA_SUCCESS ); // should be PSA_ERROR_BAD_STATE:#183
@@ -3640,7 +3640,7 @@
     PSA_ASSERT( psa_generator_abort( &generator ) );
 
     TEST_ASSERT( psa_generator_read( &generator, output_buffer, buffer_size )
-                 == PSA_ERROR_INSUFFICIENT_CAPACITY ); // should be PSA_ERROR_BAD_STATE:#183
+                 == PSA_ERROR_INSUFFICIENT_DATA ); // should be PSA_ERROR_BAD_STATE:#183
 
     TEST_ASSERT( psa_get_generator_capacity( &generator, &capacity )
                  == PSA_SUCCESS );// should be PSA_ERROR_BAD_STATE:#183
@@ -3713,14 +3713,14 @@
         {
             /* Reading 0 bytes when 0 bytes are available can go either way. */
             TEST_ASSERT( status == PSA_SUCCESS ||
-                         status == PSA_ERROR_INSUFFICIENT_CAPACITY );
+                         status == PSA_ERROR_INSUFFICIENT_DATA );
             continue;
         }
         else if( expected_capacity == 0 ||
                  output_sizes[i] > expected_capacity )
         {
             /* Capacity exceeded. */
-            TEST_EQUAL( status, PSA_ERROR_INSUFFICIENT_CAPACITY );
+            TEST_EQUAL( status, PSA_ERROR_INSUFFICIENT_DATA );
             expected_capacity = 0;
             continue;
         }
@@ -3797,7 +3797,7 @@
 
     /* Check that the generator refuses to go over capacity. */
     TEST_EQUAL( psa_generator_read( &generator, output_buffer, 1 ),
-                PSA_ERROR_INSUFFICIENT_CAPACITY );
+                PSA_ERROR_INSUFFICIENT_DATA );
 
     PSA_ASSERT( psa_generator_abort( &generator ) );
 
@@ -4033,7 +4033,7 @@
     PSA_ASSERT( psa_generator_read( &generator,
                                     output, actual_capacity ) );
     TEST_EQUAL( psa_generator_read( &generator, output, 1 ),
-                PSA_ERROR_INSUFFICIENT_CAPACITY );
+                PSA_ERROR_INSUFFICIENT_DATA );
 
 exit:
     psa_generator_abort( &generator );
@@ -4161,7 +4161,7 @@
     psa_key_type_t got_type;
     size_t got_bits;
     psa_status_t expected_info_status =
-        expected_status == PSA_SUCCESS ? PSA_SUCCESS : PSA_ERROR_EMPTY_SLOT;
+        expected_status == PSA_SUCCESS ? PSA_SUCCESS : PSA_ERROR_DOES_NOT_EXIST;
     psa_key_policy_t policy = PSA_KEY_POLICY_INIT;
 
     PSA_ASSERT( psa_crypto_init( ) );
diff --git a/tests/suites/test_suite_psa_crypto_persistent_key.function b/tests/suites/test_suite_psa_crypto_persistent_key.function
index e19ef2b..2fa307e 100644
--- a/tests/suites/test_suite_psa_crypto_persistent_key.function
+++ b/tests/suites/test_suite_psa_crypto_persistent_key.function
@@ -138,7 +138,7 @@
     /* Check key slot storage is removed */
     TEST_EQUAL( psa_is_key_present_in_storage( key_id ), 0 );
     TEST_EQUAL( psa_open_key( PSA_KEY_LIFETIME_PERSISTENT, key_id, &handle ),
-                PSA_ERROR_EMPTY_SLOT );
+                PSA_ERROR_DOES_NOT_EXIST );
     TEST_EQUAL( handle, 0 );
 
     /* Shutdown and restart */
diff --git a/tests/suites/test_suite_psa_crypto_slot_management.data b/tests/suites/test_suite_psa_crypto_slot_management.data
index c545617..e937465 100644
--- a/tests/suites/test_suite_psa_crypto_slot_management.data
+++ b/tests/suites/test_suite_psa_crypto_slot_management.data
@@ -35,7 +35,7 @@
 
 Open failure: non-existent identifier
 depends_on:MBEDTLS_PSA_CRYPTO_STORAGE_C
-open_fail:PSA_KEY_LIFETIME_PERSISTENT:1:PSA_ERROR_EMPTY_SLOT
+open_fail:PSA_KEY_LIFETIME_PERSISTENT:1:PSA_ERROR_DOES_NOT_EXIST
 
 Open failure: volatile lifetime
 open_fail:PSA_KEY_LIFETIME_VOLATILE:1:PSA_ERROR_INVALID_ARGUMENT
diff --git a/tests/suites/test_suite_psa_crypto_slot_management.function b/tests/suites/test_suite_psa_crypto_slot_management.function
index 0ebdb1e..0278b88 100644
--- a/tests/suites/test_suite_psa_crypto_slot_management.function
+++ b/tests/suites/test_suite_psa_crypto_slot_management.function
@@ -178,7 +178,7 @@
             break;
         case CLOSE_BY_DESTROY:
             TEST_EQUAL( psa_open_key( lifetime, id, &handle ),
-                        PSA_ERROR_EMPTY_SLOT );
+                        PSA_ERROR_DOES_NOT_EXIST );
             break;
     }
 
@@ -223,7 +223,7 @@
 
     /* Attempt to create a new key in the same slot. */
     TEST_EQUAL( psa_create_key( lifetime, id, &handle2 ),
-                PSA_ERROR_OCCUPIED_SLOT );
+                PSA_ERROR_ALREADY_EXISTS );
     TEST_EQUAL( handle2, 0 );
 
     if( reopen_policy == CLOSE_AFTER )
@@ -436,7 +436,7 @@
 
     /* Copy the key. */
     TEST_EQUAL( psa_copy_key( source_handle, target_handle, NULL ),
-                PSA_ERROR_EMPTY_SLOT );
+                PSA_ERROR_DOES_NOT_EXIST );
 
     /* Test that the slots are unaffected. */
     PSA_ASSERT( psa_get_key_policy( source_handle, &got_policy ) );
@@ -514,7 +514,7 @@
 
     /* Copy the key. */
     TEST_EQUAL( psa_copy_key( source_handle, target_handle, NULL ),
-                PSA_ERROR_OCCUPIED_SLOT );
+                PSA_ERROR_ALREADY_EXISTS );
 
     /* Test that the target slot is unaffected. */
     PSA_ASSERT( psa_get_key_information( target_handle,
@@ -579,7 +579,7 @@
 
     /* Copy the key. */
     TEST_EQUAL( psa_copy_key( handle, handle, NULL ),
-                PSA_ERROR_OCCUPIED_SLOT );
+                PSA_ERROR_ALREADY_EXISTS );
 
     /* Test that the slot is unaffected. */
     PSA_ASSERT( psa_get_key_information( handle,
diff --git a/tests/suites/test_suite_psa_crypto_storage_file.data b/tests/suites/test_suite_psa_crypto_storage_file.data
index 730e092..4b068e1 100644
--- a/tests/suites/test_suite_psa_crypto_storage_file.data
+++ b/tests/suites/test_suite_psa_crypto_storage_file.data
@@ -24,7 +24,7 @@
 
 PSA Storage Store into preexisting location, should fail
 depends_on:MBEDTLS_FS_IO
-write_data_to_prexisting_file:"psa_key_slot_1":"deadbeef":PSA_ERROR_OCCUPIED_SLOT
+write_data_to_prexisting_file:"psa_key_slot_1":"deadbeef":PSA_ERROR_ALREADY_EXISTS
 
 PSA Storage Store, preexisting temp_location file, should succeed
 depends_on:MBEDTLS_FS_IO
@@ -40,4 +40,4 @@
 
 PSA Storage Get data size nonexistent file location, should fail
 depends_on:MBEDTLS_FS_IO
-get_file_size:"deadbeef":4:PSA_ERROR_EMPTY_SLOT:0
+get_file_size:"deadbeef":4:PSA_ERROR_DOES_NOT_EXIST:0