diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index 0684014..1149940 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -1849,6 +1849,8 @@
     }
 #endif /* MBEDTLS_PSA_CRYPTO_SE_C */
 
+    slot->status = PSA_SLOT_OCCUPIED;
+
     return PSA_SUCCESS;
 }
 
diff --git a/library/psa_crypto_core.h b/library/psa_crypto_core.h
index d406ce4..46c5775 100644
--- a/library/psa_crypto_core.h
+++ b/library/psa_crypto_core.h
@@ -33,12 +33,19 @@
  */
 int psa_can_do_hash(psa_algorithm_t hash_alg);
 
+typedef enum {
+    PSA_SLOT_EMPTY = 0,
+    PSA_SLOT_OCCUPIED,
+} psa_key_slot_status_t;
+
 /** The data structure representing a key slot, containing key material
  * and metadata for one key.
  */
 typedef struct {
     psa_core_key_attributes_t attr;
 
+    psa_key_slot_status_t status;
+
     /*
      * Number of locks on the key slot held by the library.
      *
@@ -88,7 +95,7 @@
  */
 static inline int psa_is_key_slot_occupied(const psa_key_slot_t *slot)
 {
-    return slot->attr.type != 0;
+    return slot->status == PSA_SLOT_OCCUPIED;
 }
 
 /** Test whether a key slot is locked.
diff --git a/library/psa_crypto_slot_management.c b/library/psa_crypto_slot_management.c
index 3b8a319..5ecc3a7 100644
--- a/library/psa_crypto_slot_management.c
+++ b/library/psa_crypto_slot_management.c
@@ -237,11 +237,20 @@
         data = (psa_se_key_data_storage_t *) key_data;
         status = psa_copy_key_material_into_slot(
             slot, data->slot_number, sizeof(data->slot_number));
+
+        if (status == PSA_SUCCESS) {
+            slot->status = PSA_SLOT_OCCUPIED;
+        }
         goto exit;
     }
 #endif /* MBEDTLS_PSA_CRYPTO_SE_C */
 
     status = psa_copy_key_material_into_slot(slot, key_data, key_data_length);
+    if (status != PSA_SUCCESS) {
+        goto exit;
+    }
+
+    slot->status = PSA_SLOT_OCCUPIED;
 
 exit:
     psa_free_persistent_key_data(key_data, key_data_length);
@@ -315,6 +324,7 @@
     /* Copy actual key length and core attributes into the slot on success */
     slot->key.bytes = key_buffer_length;
     slot->attr = attributes.core;
+    slot->status = PSA_SLOT_OCCUPIED;
 
 exit:
     if (status != PSA_SUCCESS) {