diff --git a/src/userfunc.c b/src/userfunc.c
index 6f0d59d..5b2c876 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -3048,7 +3048,8 @@
     // Invoke functions added with ":defer".
     handle_defer_one(current_funccal);
 
-    --RedrawingDisabled;
+    if (RedrawingDisabled > 0)
+	--RedrawingDisabled;
 
     // when the function was aborted because of an error, return -1
     if ((did_emsg && (fp->uf_flags & FC_ABORT)) || rettv->v_type == VAR_UNKNOWN)