diff --git a/src/eval.c b/src/eval.c
index e08a25a..8a573de 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -1987,8 +1987,9 @@ it defines a macro.  */)
       Lisp_Object fun = Findirect_function (funname, Qnil);
 
       if (!NILP (Fequal (fun, fundef)))
-	error ("Autoloading failed to define function %s",
-	       SDATA (SYMBOL_NAME (funname)));
+	error ("Autoloading failed to define function %s with filename %s",
+	       SDATA (SYMBOL_NAME (funname)),
+	       SDATA (Fcar (Fcdr (fundef))));
       else
 	return fun;
     }