diff --git a/include/mbedtls/cipher_internal.h b/include/mbedtls/cipher_internal.h
index f1f0e2b..cecad9a 100644
--- a/include/mbedtls/cipher_internal.h
+++ b/include/mbedtls/cipher_internal.h
@@ -119,14 +119,26 @@
 } mbedtls_cipher_definition_t;
 
 #if defined(MBEDTLS_USE_PSA_CRYPTO)
+typedef enum
+{
+    MBEDTLS_CIPHER_PSA_KEY_UNSET = 0,
+    MBEDTLS_CIPHER_PSA_KEY_OWNED, /* Used for PSA-based cipher contexts
+                                   * which use raw key material internally
+                                   * imported into a freshly allocated key slot,
+                                   * and which hence need to destroy that key
+                                   * slot when they are no longer needed. */
+    MBEDTLS_CIPHER_PSA_KEY_NOT_OWNED, /* Used for PSA-based cipher contexts
+                                       * which use a key from a key slot
+                                       * provided by the user, and which hence
+                                       * should not be destroyed when the
+                                       * context is no longer needed. */
+} mbedtls_cipher_psa_key_ownership;
+
 typedef struct
 {
     psa_algorithm_t alg;
     psa_key_slot_t slot;
-    unsigned char slot_state; /*!< 0: The slot is unset.
-                               *   1: The slot is set and we own it.
-                               *   2: The slot is set but we don't own it. */
-
+    mbedtls_cipher_psa_key_ownership slot_state;
 } mbedtls_cipher_context_psa;
 #endif /* MBEDTLS_USE_PSA_CRYPTO */
 
diff --git a/library/cipher.c b/library/cipher.c
index e9a1a07..95146ac 100644
--- a/library/cipher.c
+++ b/library/cipher.c
@@ -175,7 +175,7 @@
             mbedtls_cipher_context_psa * const cipher_psa =
                 (mbedtls_cipher_context_psa *) ctx->cipher_ctx;
 
-            if( cipher_psa->slot_state == 1 )
+            if( cipher_psa->slot_state == MBEDTLS_CIPHER_PSA_KEY_OWNED )
             {
                 /* xxx_free() doesn't allow to return failures. */
                 (void) psa_destroy_key( cipher_psa->slot );
@@ -299,14 +299,16 @@
             return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
 
         /* Don't allow keys to be set multiple times. */
-        if( cipher_psa->slot_state != 0 )
+        if( cipher_psa->slot_state != MBEDTLS_CIPHER_PSA_KEY_UNSET )
             return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
 
         /* Find a fresh key slot to use. */
         status = mbedtls_psa_get_free_key_slot( &cipher_psa->slot );
         if( status != PSA_SUCCESS )
             return( MBEDTLS_ERR_CIPHER_HW_ACCEL_FAILED );
-        cipher_psa->slot_state = 1; /* Indicate that we own the key slot. */
+         /* Indicate that we own the key slot and need to
+          * destroy it in mbedtls_cipher_free(). */
+        cipher_psa->slot_state = MBEDTLS_CIPHER_PSA_KEY_OWNED;
 
         /* From that point on, the responsibility for destroying the
          * key slot is on mbedtls_cipher_free(). This includes the case