diff --git a/src/main/scala/view/AvatarImageProvider.scala b/src/main/scala/view/AvatarImageProvider.scala
index fda49c0..bcc2d6b 100644
--- a/src/main/scala/view/AvatarImageProvider.scala
+++ b/src/main/scala/view/AvatarImageProvider.scala
@@ -17,7 +17,7 @@
       // by user name
       getAccountByUserName(userName).map { account =>
         if(account.image.isEmpty && getSystemSettings().gravatar){
-          s"""http://www.gravatar.com/avatar/${StringUtil.md5(account.mailAddress.toLowerCase)}?s=${size}"""
+          s"""https://www.gravatar.com/avatar/${StringUtil.md5(account.mailAddress.toLowerCase)}?s=${size}"""
         } else {
           s"""${context.path}/${account.userName}/_avatar"""
         }
@@ -28,13 +28,13 @@
       // by mail address
       getAccountByMailAddress(mailAddress).map { account =>
         if(account.image.isEmpty && getSystemSettings().gravatar){
-          s"""http://www.gravatar.com/avatar/${StringUtil.md5(account.mailAddress.toLowerCase)}?s=${size}"""
+          s"""https://www.gravatar.com/avatar/${StringUtil.md5(account.mailAddress.toLowerCase)}?s=${size}"""
         } else {
           s"""${context.path}/${account.userName}/_avatar"""
         }
       } getOrElse {
         if(getSystemSettings().gravatar){
-          s"""http://www.gravatar.com/avatar/${StringUtil.md5(mailAddress.toLowerCase)}?s=${size}"""
+          s"""https://www.gravatar.com/avatar/${StringUtil.md5(mailAddress.toLowerCase)}?s=${size}"""
         } else {
           s"""${context.path}/_unknown/_avatar"""
         }
diff --git a/src/test/scala/view/AvatarImageProviderSpec.scala b/src/test/scala/view/AvatarImageProviderSpec.scala
index 8b9dcd5..d5e5775 100644
--- a/src/test/scala/view/AvatarImageProviderSpec.scala
+++ b/src/test/scala/view/AvatarImageProviderSpec.scala
@@ -17,7 +17,7 @@
       val provider = new AvatarImageProviderImpl(Some(createAccount(None)), createSystemSettings(true))
 
       provider.toHtml("user", 20).toString mustEqual
-        "<img src=\"http://www.gravatar.com/avatar/d41d8cd98f00b204e9800998ecf8427e?s=20\" class=\"avatar\" style=\"width: 20px; height: 20px;\" />"
+        "<img src=\"https://www.gravatar.com/avatar/d41d8cd98f00b204e9800998ecf8427e?s=20\" class=\"avatar\" style=\"width: 20px; height: 20px;\" />"
     }
 
     "show uploaded image even if gravatar integration is enabled" in {
@@ -38,7 +38,7 @@
       val provider = new AvatarImageProviderImpl(None, createSystemSettings(true))
 
       provider.toHtml("user", 20, "hoge@hoge.com").toString mustEqual
-        "<img src=\"http://www.gravatar.com/avatar/4712f9b0e63f56ad952ad387eaa23b9c?s=20\" class=\"avatar\" style=\"width: 20px; height: 20px;\" />"
+        "<img src=\"https://www.gravatar.com/avatar/4712f9b0e63f56ad952ad387eaa23b9c?s=20\" class=\"avatar\" style=\"width: 20px; height: 20px;\" />"
     }
 
     "show unknown image for unknown user if gravatar integration is enabled" in {