diff --git a/src/ex_cmds.c b/src/ex_cmds.c
index 53c7bb5..4f1d932 100644
--- a/src/ex_cmds.c
+++ b/src/ex_cmds.c
@@ -4651,7 +4651,7 @@
 		mch_memmove(new_end, sub_firstline + copycol, (size_t)copy_len);
 		new_end += copy_len;
 
-		if (new_start_len - copy_len < sublen)
+		if ((int)new_start_len - copy_len < sublen)
 		    sublen = new_start_len - copy_len - 1;
 
 #ifdef FEAT_EVAL