1 files changed, 1 insertions, 1 deletions
diff --git a/pop3.c b/pop3.c
index fc574f64..1a74715a 100644
--- a/pop3.c
+++ b/pop3.c
@@ -148,7 +148,7 @@ static int pop3_ok (int sock, char *argbuf)
 	else
 	    return(PS_PROTOCOL);
 
-	while (isalpha(*bufp))
+	while (isalpha((unsigned char)*bufp))
 	    bufp++;
 
 	if (*bufp)