diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index bbd6b24ed4..0660ee411b 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -1786,6 +1786,7 @@ static psa_status_t psa_start_key_creation(
      * definition. */
 
     slot->attr = attributes->core;
+    slot->status = PSA_SLOT_OCCUPIED;
     if (PSA_KEY_LIFETIME_IS_VOLATILE(slot->attr.lifetime)) {
 #if !defined(MBEDTLS_PSA_CRYPTO_KEY_ID_ENCODES_OWNER)
         slot->attr.id = volatile_key_id;
diff --git a/library/psa_crypto_core.h b/library/psa_crypto_core.h
index d406ce459d..700e0fef66 100644
--- a/library/psa_crypto_core.h
+++ b/library/psa_crypto_core.h
@@ -39,6 +39,11 @@ int psa_can_do_hash(psa_algorithm_t hash_alg);
 typedef struct {
     psa_core_key_attributes_t attr;
 
+    enum {
+        PSA_SLOT_EMPTY = 0,
+        PSA_SLOT_OCCUPIED,
+    } status;
+
     /*
      * Number of locks on the key slot held by the library.
      *
@@ -88,7 +93,7 @@ typedef struct {
  */
 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 3b8a319cbb..36d541044a 100644
--- a/library/psa_crypto_slot_management.c
+++ b/library/psa_crypto_slot_management.c
@@ -221,6 +221,7 @@ static psa_status_t psa_load_persistent_key_into_slot(psa_key_slot_t *slot)
     if (status != PSA_SUCCESS) {
         goto exit;
     }
+    slot->status = PSA_SLOT_OCCUPIED;
 
 #if defined(MBEDTLS_PSA_CRYPTO_SE_C)
     /* Special handling is required for loading keys associated with a
@@ -315,6 +316,7 @@ static psa_status_t psa_load_builtin_key_into_slot(psa_key_slot_t *slot)
     /* 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) {