1 files changed, 4 insertions, 1 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/query2/engine/Callback.java b/src/main/java/com/google/devtools/build/lib/query2/engine/Callback.java
index 0f4321145d..51c51fa99b 100644
--- a/src/main/java/com/google/devtools/build/lib/query2/engine/Callback.java
+++ b/src/main/java/com/google/devtools/build/lib/query2/engine/Callback.java
@@ -13,14 +13,17 @@
 // limitations under the License.
 package com.google.devtools.build.lib.query2.engine;
 
+import com.google.devtools.build.lib.concurrent.ThreadSafety.ThreadSafe;
 import com.google.devtools.build.lib.util.BatchCallback;
+import com.google.devtools.build.lib.util.ThreadSafeBatchCallback;
 
 /**
  * Query callback to be called by a {@link QueryExpression} when it has part of the computation
  * result. Assuming the {@code QueryEnvironment} supports it, it would allow the caller
  * to stream the results.
  */
-public interface Callback<T> extends BatchCallback<T, QueryException> {
+@ThreadSafe
+public interface Callback<T> extends ThreadSafeBatchCallback<T, QueryException> {
 
   /**
    * According to the {@link BatchCallback} interface, repeated elements may be passed in here.