diff --git a/code/qcommon/msg.c b/code/qcommon/msg.c
index 4ff6d63c..8fb44fdf 100644
--- a/code/qcommon/msg.c
+++ b/code/qcommon/msg.c
@@ -631,7 +631,7 @@ void MSG_WriteDeltaKey( msg_t *msg, int key, int oldV, int newV, int bits ) {
 
 int	MSG_ReadDeltaKey( msg_t *msg, int key, int oldV, int bits ) {
 	if ( MSG_ReadBits( msg, 1 ) ) {
-		return MSG_ReadBits( msg, bits ) ^ (key & kbitmask[bits]);
+		return MSG_ReadBits( msg, bits ) ^ (key & kbitmask[ bits - 1 ]);
 	}
 	return oldV;
 }