diff --git a/lib/port.c b/lib/port.c
index bda19444..6f054932 100644
--- a/lib/port.c
+++ b/lib/port.c
@@ -144,23 +144,19 @@ next:
 	 * TTY devices.
 	 */
 
+	if (strchr(buf, ':') == NULL)
+		goto next;
+
 	port.pt_names = ttys;
 	for (cp = buf, j = 0; j < PORT_TTY; j++) {
 		port.pt_names[j] = cp;
 		cp = strpbrk(cp, ":,");
-		if (cp == NULL)
-			goto next;	/* line format error */
-
-		if (':' == *cp) {	/* end of tty name list */
+		if (':' == *cp)		/* end of tty name list */
 			break;
-		}
-
-		if (',' == *cp) {	/* end of current tty name */
-			*cp++ = '\0';
-		}
+		if (',' == *cp)		/* end of current tty name */
+			stpcpy(cp++, "");
 	}
-	*cp = '\0';
-	cp++;
+	stpcpy(cp++, "");
 	port.pt_names[j] = NULL;
 
 	/*
@@ -170,6 +166,9 @@ next:
 	 * The last entry in the list is a NULL pointer.
 	 */
 
+	if (strchr(cp, ':') == NULL)
+		goto next;
+
 	if (':' != *cp) {
 		port.pt_users = users;
 		port.pt_users[0] = cp;