diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index 64ab247..e51f849 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -2747,7 +2747,7 @@
     for (i = 0; cmd[i] != NUL; ++i)
 	if (((char_u *)cmd)[i] != (*pp)[i])
 	    break;
-    if (i >= len && !isalpha((*pp)[i]) && (*pp)[i] != '_'
+    if (i >= len && !ASCII_ISALPHA((*pp)[i]) && (*pp)[i] != '_'
 			 && (!noparen || ((*pp)[i] != '(' && (*pp)[i] != '.')))
     {
 	*pp = skipwhite(*pp + i);