diff --git a/packages/MtpDocumentsProvider/Android.mk b/packages/MtpDocumentsProvider/Android.mk
index b31b0b13ec070..0f945ee8a5e16 100644
--- a/packages/MtpDocumentsProvider/Android.mk
+++ b/packages/MtpDocumentsProvider/Android.mk
@@ -9,5 +9,10 @@ LOCAL_PRIVILEGED_MODULE := true
 LOCAL_JNI_SHARED_LIBRARIES := libappfuse_jni
 LOCAL_PROGUARD_FLAG_FILES := proguard.flags
 
+# Only enable asserts on userdebug/eng builds
+ifneq (,$(filter userdebug eng, $(TARGET_BUILD_VARIANT)))
+LOCAL_JACK_FLAGS += -D jack.assert.policy=enable
+endif
+
 include $(BUILD_PACKAGE)
 include $(call all-makefiles-under, $(LOCAL_PATH))
diff --git a/packages/MtpDocumentsProvider/src/com/android/mtp/DocumentLoader.java b/packages/MtpDocumentsProvider/src/com/android/mtp/DocumentLoader.java
index c42cf20c14b03..68f426fa61767 100644
--- a/packages/MtpDocumentsProvider/src/com/android/mtp/DocumentLoader.java
+++ b/packages/MtpDocumentsProvider/src/com/android/mtp/DocumentLoader.java
@@ -69,7 +69,8 @@ class DocumentLoader implements AutoCloseable {
      */
     synchronized Cursor queryChildDocuments(String[] columnNames, Identifier parent)
             throws IOException {
-        Preconditions.checkArgument(parent.mDeviceId == mDevice.deviceId);
+        assert parent.mDeviceId == mDevice.deviceId;
+
         LoaderTask task = mTaskList.findTask(parent);
         if (task == null) {
             if (parent.mDocumentId == null) {
@@ -256,7 +257,8 @@ class DocumentLoader implements AutoCloseable {
 
         LoaderTask(MtpManager manager, MtpDatabase database, int[] operationsSupported,
                 Identifier identifier) {
-            Preconditions.checkNotNull(operationsSupported);
+            assert operationsSupported != null;
+            assert identifier.mDocumentType != MtpDatabaseConstants.DOCUMENT_TYPE_DEVICE;
             mManager = manager;
             mDatabase = database;
             mOperationsSupported = operationsSupported;
diff --git a/packages/MtpDocumentsProvider/src/com/android/mtp/MtpDatabase.java b/packages/MtpDocumentsProvider/src/com/android/mtp/MtpDatabase.java
index f901ff05deb32..4564018f57608 100644
--- a/packages/MtpDocumentsProvider/src/com/android/mtp/MtpDatabase.java
+++ b/packages/MtpDocumentsProvider/src/com/android/mtp/MtpDatabase.java
@@ -617,6 +617,7 @@ class MtpDatabase {
         final String whereClosure =
                 "parent." + COLUMN_DEVICE_ID + " = ? AND " +
                 "parent." + COLUMN_ROW_STATE + " IN (?, ?) AND " +
+                "parent." + COLUMN_DOCUMENT_TYPE + " != ? AND " +
                 "child." + COLUMN_ROW_STATE + " = ?";
         try (final Cursor cursor = mDatabase.query(
                 fromClosure,
@@ -626,7 +627,7 @@ class MtpDatabase {
                         "parent." + Document.COLUMN_DOCUMENT_ID,
                         "parent." + COLUMN_DOCUMENT_TYPE),
                 whereClosure,
-                strings(deviceId, ROW_STATE_VALID, ROW_STATE_INVALIDATED,
+                strings(deviceId, ROW_STATE_VALID, ROW_STATE_INVALIDATED, DOCUMENT_TYPE_DEVICE,
                         ROW_STATE_DISCONNECTED),
                 null,
                 null,