diff --git a/qjson.c b/qjson.c
index 9ad8a91..0922c06 100644
--- a/qjson.c
+++ b/qjson.c
@@ -62,6 +62,7 @@ QObject *qobject_from_jsonf(const char *string, ...)
     obj = qobject_from_jsonv(string, &ap);
     va_end(ap);
 
+    assert(obj != NULL);
     return obj;
 }