diff --git a/appl/telnet/telnet/ring.c b/appl/telnet/telnet/ring.c
index fb468a97c..f4aee9ed7 100644
--- a/appl/telnet/telnet/ring.c
+++ b/appl/telnet/telnet/ring.c
@@ -288,7 +288,7 @@ ring_consume_data(Ring *ring, unsigned char *buffer, int count)
 
 #if	defined(ENCRYPTION)
 void
-ring_encrypt(Ring *ring, void (*encryptor)())
+ring_encrypt(Ring *ring, void (*encryptor)(unsigned char *, int))
 {
     unsigned char *s, *c;
 
diff --git a/appl/telnet/telnet/ring.h b/appl/telnet/telnet/ring.h
index 12b9341a1..04e3eaebd 100644
--- a/appl/telnet/telnet/ring.h
+++ b/appl/telnet/telnet/ring.h
@@ -88,7 +88,7 @@ extern int
 
 #if	defined(ENCRYPTION)
 extern void
-	ring_encrypt (Ring *ring, void (*func)()),
+	ring_encrypt (Ring *ring, void (*func)(unsigned char *, int)),
 	ring_clearto (Ring *ring);
 #endif