diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index c4f41db..696e830 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -705,6 +705,17 @@
 psa_status_t psa_allocate_buffer_to_slot(psa_key_slot_t *slot,
                                          size_t buffer_length)
 {
+#if defined(MBEDTLS_PSA_STATIC_KEY_SLOTS)
+    if (slot->key.in_use) {
+        return PSA_ERROR_ALREADY_EXISTS;
+    }
+
+    if (buffer_length > ((size_t) MBEDTLS_PSA_STATIC_KEY_SLOT_BUFFER_SIZE)) {
+        return PSA_ERROR_NOT_SUPPORTED;
+    }
+
+    slot->key.in_use = 1;
+#else
     if (slot->key.data != NULL) {
         return PSA_ERROR_ALREADY_EXISTS;
     }
@@ -713,6 +724,7 @@
     if (slot->key.data == NULL) {
         return PSA_ERROR_INSUFFICIENT_MEMORY;
     }
+#endif
 
     slot->key.bytes = buffer_length;
     return PSA_SUCCESS;
@@ -1177,11 +1189,16 @@
 
 psa_status_t psa_remove_key_data_from_memory(psa_key_slot_t *slot)
 {
+#if defined(MBEDTLS_PSA_STATIC_KEY_SLOTS)
+    slot->key.in_use = 0;
+#else /* MBEDTLS_PSA_STATIC_KEY_SLOTS */
     if (slot->key.data != NULL) {
         mbedtls_zeroize_and_free(slot->key.data, slot->key.bytes);
     }
 
     slot->key.data = NULL;
+#endif /* MBEDTLS_PSA_STATIC_KEY_SLOTS */
+
     slot->key.bytes = 0;
 
     return PSA_SUCCESS;
@@ -2096,7 +2113,13 @@
      * storage ( thus not in the case of importing a key in a secure element
      * with storage ( MBEDTLS_PSA_CRYPTO_SE_C ) ),we have to allocate a
      * buffer to hold the imported key material. */
-    if (slot->key.data == NULL) {
+#if defined(MBEDTLS_PSA_STATIC_KEY_SLOTS)
+    int is_slot_unused = (slot->key.in_use == 0);
+#else
+    int is_slot_unused = (slot->key.data == NULL);
+#endif
+
+    if (is_slot_unused) {
         if (psa_key_lifetime_is_external(attributes->lifetime)) {
             status = psa_driver_wrapper_get_key_buffer_size_from_key_data(
                 attributes, data, data_length, &storage_size);
@@ -8013,7 +8036,13 @@
      * storage ( thus not in the case of generating a key in a secure element
      * with storage ( MBEDTLS_PSA_CRYPTO_SE_C ) ),we have to allocate a
      * buffer to hold the generated key material. */
-    if (slot->key.data == NULL) {
+#if defined(MBEDTLS_PSA_STATIC_KEY_SLOTS)
+    int is_slot_unused = (slot->key.in_use == 0);
+#else
+    int is_slot_unused = (slot->key.data == NULL);
+#endif
+
+    if (is_slot_unused) {
         if (PSA_KEY_LIFETIME_GET_LOCATION(attributes->lifetime) ==
             PSA_KEY_LOCATION_LOCAL_STORAGE) {
             status = psa_validate_key_type_and_size_for_key_generation(