diff --git a/notify.c b/notify.c
index f8c2bfe1..b16b941b 100644
--- a/notify.c
+++ b/notify.c
@@ -63,8 +63,10 @@ consume_stdout(struct notification *notif, bool eof)
         left -= len + (eol != NULL ? 1 : 0);
     }
 
-    memmove(notif->stdout_data, data, left);
-    notif->stdout_sz = left;
+    if (left > 0) {
+        memmove(notif->stdout_data, data, left);
+        notif->stdout_sz = left;
+    }
 }
 
 static bool