diff --git a/src/main/java/com/googlesource/gerrit/plugins/cfoauth/CFOAuthService.java b/src/main/java/com/googlesource/gerrit/plugins/cfoauth/CFOAuthService.java
index 75ffe0d..b5b294e 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/cfoauth/CFOAuthService.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/cfoauth/CFOAuthService.java
@@ -143,7 +143,7 @@
   }
 
   private static OAuthUserInfo getAsOAuthUserInfo(String username) {
-    return new OAuthUserInfo(SCHEME_EXTERNAL + username,
+    return new OAuthUserInfo(SCHEME_EXTERNAL + ":" + username,
         username, null, null, null);
   }
 }
diff --git a/src/main/java/com/googlesource/gerrit/plugins/cfoauth/UserInfo.java b/src/main/java/com/googlesource/gerrit/plugins/cfoauth/UserInfo.java
index 62ce5a0..d539301 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/cfoauth/UserInfo.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/cfoauth/UserInfo.java
@@ -42,7 +42,7 @@
       throw new IllegalArgumentException("emailAddress must not be null");
     }
     this.username = username;
-    this.externalId = SCHEME_EXTERNAL + username;
+    this.externalId = SCHEME_EXTERNAL + ":" + username;
     this.emailAddress = emailAddress;
     this.displayName = username;
   }