diff --git a/usr.bin/mail/lex.c b/usr.bin/mail/lex.c
index 4550f2b0a70..c80b46b1141 100644
--- a/usr.bin/mail/lex.c
+++ b/usr.bin/mail/lex.c
@@ -188,7 +188,7 @@ commands()
 		 */
 		if (!sourcing && value("interactive") != NOSTR) {
 			reset_on_stop = 1;
-			printf(prompt);
+			printf("%s", prompt);
 		}
 		fflush(stdout);
 		sreset();