diff --git a/oak-auth-external/src/main/java/org/apache/jackrabbit/oak/spi/security/authentication/external/basic/DefaultSyncContext.java b/oak-auth-external/src/main/java/org/apache/jackrabbit/oak/spi/security/authentication/external/basic/DefaultSyncContext.java
index 643ba3c..f264e01 100644
--- a/oak-auth-external/src/main/java/org/apache/jackrabbit/oak/spi/security/authentication/external/basic/DefaultSyncContext.java
+++ b/oak-auth-external/src/main/java/org/apache/jackrabbit/oak/spi/security/authentication/external/basic/DefaultSyncContext.java
@@ -120,6 +120,9 @@ public class DefaultSyncContext implements SyncContext {
             return null;
         }
         ExternalIdentityRef ref = getIdentityRef(auth);
+        if (ref == null) {
+            return null;
+        }
         Value[] lmValues = auth.getProperty(REP_LAST_SYNCED);
         long lastModified = -1;
         if (lmValues != null && lmValues.length > 0) {