diff --git a/crypto/time.go b/crypto/time.go
index eeb91c9..85b0fff 100644
--- a/crypto/time.go
+++ b/crypto/time.go
@@ -7,8 +7,10 @@ import (
 
 // UpdateTime updates cached time.
 func UpdateTime(newTime int64) {
-	pgp.latestServerTime = newTime
-	pgp.latestClientTime = time.Now()
+	if newTime > pgp.latestServerTime {
+		pgp.latestServerTime = newTime
+		pgp.latestClientTime = time.Now()
+	}
 }
 
 // GetUnixTime gets latest cached time.