diff --git a/mux.c b/mux.c
index 1cfb914..1741efe 100644
--- a/mux.c
+++ b/mux.c
@@ -211,7 +211,7 @@ char *answerback;
 
 static void write_receive_buf(const unsigned char *buf, int len)
 {
-	if (!len)
+	if (len <= 0)
 		return;
 
 	write(STDOUT_FILENO, buf, len);
@@ -306,7 +306,7 @@ static int handle_receive_buf(struct ios_ops *ios, unsigned char *buf, int len)
 	unsigned char *sendbuf = buf;
 	int i;
 
-	while (len) {
+	while (len > 0) {
 		switch (*buf) {
 		case IAC:
 			/* BUG: this is telnet specific */