diff --git a/src/main/java/com/googlesource/gerrit/plugins/avatars/external/ExternalUrlAvatarProvider.java b/src/main/java/com/googlesource/gerrit/plugins/avatars/external/ExternalUrlAvatarProvider.java
index fdac920..dd03c91 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/avatars/external/ExternalUrlAvatarProvider.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/avatars/external/ExternalUrlAvatarProvider.java
@@ -99,7 +99,7 @@
   @Override
   public String getChangeAvatarUrl(IdentifiedUser forUser) {
     String userReplacedAvatarChangeURL = replaceInUrl(USER_PLACEHOLDER,
-        avatarChangeUrl, forUser.getUserName().get());
+        avatarChangeUrl, forUser.getUserName().orElse(null));
     return replaceInUrl(EMAIL_PLACEHOLDER, userReplacedAvatarChangeURL,
         forUser.getAccount().getPreferredEmail());
   }