diff --git a/interop-testing/src/main/java/io/grpc/testing/integration/TestServiceImpl.java b/interop-testing/src/main/java/io/grpc/testing/integration/TestServiceImpl.java
index 5fe7248b2b..8d0c4f421a 100644
--- a/interop-testing/src/main/java/io/grpc/testing/integration/TestServiceImpl.java
+++ b/interop-testing/src/main/java/io/grpc/testing/integration/TestServiceImpl.java
@@ -228,7 +228,7 @@ public class TestServiceImpl extends TestServiceGrpc.TestServiceImplBase {
   private class ResponseDispatcher {
     private final Chunk completionChunk = new Chunk(0, 0, 0);
     private final Queue<Chunk> chunks;
-    private final StreamObserver<StreamingOutputCallResponse> responseStream;
+    private final ServerCallStreamObserver<StreamingOutputCallResponse> responseStream;
     private boolean scheduled;
     @GuardedBy("this") private boolean cancelled;
     private Throwable failure;
@@ -268,7 +268,12 @@ public class TestServiceImpl extends TestServiceGrpc.TestServiceImplBase {
      */
     public ResponseDispatcher(StreamObserver<StreamingOutputCallResponse> responseStream) {
       this.chunks = Queues.newLinkedBlockingQueue();
-      this.responseStream = responseStream;
+      this.responseStream = (ServerCallStreamObserver<StreamingOutputCallResponse>) responseStream;
+      this.responseStream.setOnReadyHandler(new Runnable() {
+        @Override public void run() {
+          scheduleNextChunk();
+        }
+      });
     }
 
     /**
@@ -349,6 +354,11 @@ public class TestServiceImpl extends TestServiceGrpc.TestServiceImplBase {
           return;
         }
 
+        if (chunks.peek() != completionChunk && !responseStream.isReady()) {
+          // Wait for the onReady handler to be called.
+          return;
+        }
+
         // Schedule the next response chunk if there is one.
         Chunk nextChunk = chunks.peek();
         if (nextChunk != null) {