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 );