diff --git a/src/sbbs3/wordwrap.c b/src/sbbs3/wordwrap.c
index 1c739e4154b2790750310499c767d022a0c391b2..50dbf738c2016db677253081f1ed3bd39b42af49 100644
--- a/src/sbbs3/wordwrap.c
+++ b/src/sbbs3/wordwrap.c
@@ -211,7 +211,7 @@ static struct section_len get_ws_len(char *buf, int col)
 	for(ret.bytes=0; ; ret.bytes++) {
 		if (!buf[ret.bytes])
 			break;
-		if (!isspace(buf[ret.bytes]))
+		if (!isspace((unsigned char)buf[ret.bytes]))
 			break;
 		if(buf[ret.bytes] == '\t') {
 			ret.len++;