diff --git a/backends/cryptodev-builtin.c b/backends/cryptodev-builtin.c
index 39d0455280..a514bbb310 100644
--- a/backends/cryptodev-builtin.c
+++ b/backends/cryptodev-builtin.c
@@ -427,7 +427,9 @@ static int cryptodev_builtin_close_session(
                       CRYPTODEV_BACKEND_BUILTIN(backend);
     CryptoDevBackendBuiltinSession *session;
 
-    assert(session_id < MAX_NUM_SESSIONS && builtin->sessions[session_id]);
+    if (session_id >= MAX_NUM_SESSIONS || !builtin->sessions[session_id]) {
+        return -VIRTIO_CRYPTO_INVSESS;
+    }
 
     session = builtin->sessions[session_id];
     if (session->cipher) {