diff --git a/gerrit-reviewdb/src/main/java/com/google/gerrit/reviewdb/client/AccountGroup.java b/gerrit-reviewdb/src/main/java/com/google/gerrit/reviewdb/client/AccountGroup.java
index 2ea659db61..061ef3e42e 100644
--- a/gerrit-reviewdb/src/main/java/com/google/gerrit/reviewdb/client/AccountGroup.java
+++ b/gerrit-reviewdb/src/main/java/com/google/gerrit/reviewdb/client/AccountGroup.java
@@ -82,7 +82,7 @@ public final class AccountGroup {
   /** @return true if the UUID is for a group managed within Gerrit. */
   public static boolean isInternalGroup(AccountGroup.UUID uuid) {
     return uuid.get().startsWith("global:")
-        || uuid.get().matches("[0-9a-f]{40}");
+        || uuid.get().matches("^[0-9a-f]{40}$");
   }
 
   /** Synthetic key to link to within the database */