diff --git a/models/user.go b/models/user.go
index ffee2dd9..ab43df7a 100644
--- a/models/user.go
+++ b/models/user.go
@@ -76,7 +76,7 @@ func (user *User) AvatarLink() string {
 	if base.Service.EnableCacheAvatar {
 		return "/avatar/" + user.Avatar
 	}
-	return "http://1.gravatar.com/avatar/" + user.Avatar
+	return "//1.gravatar.com/avatar/" + user.Avatar
 }
 
 // NewGitSig generates and returns the signature of given user.
diff --git a/modules/base/tool.go b/modules/base/tool.go
index 082c0392..9b165b97 100644
--- a/modules/base/tool.go
+++ b/modules/base/tool.go
@@ -143,7 +143,7 @@ func AvatarLink(email string) string {
 	if Service.EnableCacheAvatar {
 		return "/avatar/" + EncodeMd5(email)
 	}
-	return "http://1.gravatar.com/avatar/" + EncodeMd5(email)
+	return "//1.gravatar.com/avatar/" + EncodeMd5(email)
 }
 
 // Seconds-based time units