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 ca5444f..056a1f2 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
@@ -114,7 +114,7 @@
    */
   private String replaceInUrl(String placeholder, String url,
       String replacement) {
-    if (!url.contains(placeholder)) {
+    if (url == null || !url.contains(placeholder)) {
       return url;
     }