diff --git a/qjson.c b/qjson.c
index 9ad8a91208e24f4ed3c57b04ccd4396445185625..483c6675db72cf25f347be176c0e3d8e073d6175 100644
--- a/qjson.c
+++ b/qjson.c
@@ -53,6 +53,10 @@ QObject *qobject_from_json(const char *string)
     return qobject_from_jsonv(string, NULL);
 }
 
+/*
+ * IMPORTANT: This function aborts on error, thus it must not
+ * be used with untrusted arguments.
+ */
 QObject *qobject_from_jsonf(const char *string, ...)
 {
     QObject *obj;
@@ -62,6 +66,7 @@ QObject *qobject_from_jsonf(const char *string, ...)
     obj = qobject_from_jsonv(string, &ap);
     va_end(ap);
 
+    assert(obj != NULL);
     return obj;
 }