diff --git a/src/ui.c b/src/ui.c
index 08664bf..8368c30 100644
--- a/src/ui.c
+++ b/src/ui.c
@@ -897,7 +897,8 @@
 	maxlen = inbufcount;
     mch_memmove(buf, inbuf, (size_t)maxlen);
     inbufcount -= maxlen;
-    if (inbufcount)
+    // check "maxlen" to avoid clang warning
+    if (inbufcount > 0 && maxlen > 0)
 	mch_memmove(inbuf, inbuf + maxlen, (size_t)inbufcount);
     return (int)maxlen;
 }