diff --git a/service-t/src/com/android/server/NsdService.java b/service-t/src/com/android/server/NsdService.java
index 53782ac..f7edbe4 100644
--- a/service-t/src/com/android/server/NsdService.java
+++ b/service-t/src/com/android/server/NsdService.java
@@ -1920,11 +1920,14 @@
     @Override
     public INsdServiceConnector connect(INsdManagerCallback cb, boolean useJavaBackend) {
         mContext.enforceCallingOrSelfPermission(android.Manifest.permission.INTERNET, "NsdService");
+        final int uid = mDeps.getCallingUid();
+        if (cb == null) {
+            throw new IllegalArgumentException("Unknown client callback from uid=" + uid);
+        }
         if (DBG) Log.d(TAG, "New client connect. useJavaBackend=" + useJavaBackend);
         final INsdServiceConnector connector = new NsdServiceConnector();
         mNsdStateMachine.sendMessage(mNsdStateMachine.obtainMessage(NsdManager.REGISTER_CLIENT,
-                new ConnectorArgs((NsdServiceConnector) connector, cb, useJavaBackend,
-                        mDeps.getCallingUid())));
+                new ConnectorArgs((NsdServiceConnector) connector, cb, useJavaBackend, uid)));
         return connector;
     }
 
diff --git a/tests/unit/java/com/android/server/NsdServiceTest.java b/tests/unit/java/com/android/server/NsdServiceTest.java
index 55384b3..f778075 100644
--- a/tests/unit/java/com/android/server/NsdServiceTest.java
+++ b/tests/unit/java/com/android/server/NsdServiceTest.java
@@ -1585,6 +1585,20 @@
         lockOrder.verify(mMulticastLock).release();
     }
 
+    @Test
+    public void testNullINsdManagerCallback() {
+        final NsdService service = new NsdService(mContext, mHandler, CLEANUP_DELAY_MS, mDeps) {
+            @Override
+            public INsdServiceConnector connect(INsdManagerCallback baseCb,
+                    boolean runNewMdnsBackend) {
+                // Pass null INsdManagerCallback
+                return super.connect(null /* cb */, runNewMdnsBackend);
+            }
+        };
+
+        assertThrows(IllegalArgumentException.class, () -> new NsdManager(mContext, service));
+    }
+
     private void waitForIdle() {
         HandlerUtils.waitForIdle(mHandler, TIMEOUT_MS);
     }