diff --git a/testground/benchmark/benchmark/main.py b/testground/benchmark/benchmark/main.py
index 612db1e854..bbb085700e 100644
--- a/testground/benchmark/benchmark/main.py
+++ b/testground/benchmark/benchmark/main.py
@@ -1,4 +1,3 @@
-import json
 import os
 import queue
 
diff --git a/testground/benchmark/benchmark/sync.py b/testground/benchmark/benchmark/sync.py
index 741099e2af..63d768d304 100644
--- a/testground/benchmark/benchmark/sync.py
+++ b/testground/benchmark/benchmark/sync.py
@@ -87,7 +87,7 @@ def _subscribe(self, topic, callback):
         "send one request, recv multiple responses"
 
         def on_recv(msg):
-            callback(msg["subscribe"] if msg is not None else None)
+            callback(json.loads(msg["subscribe"]) if msg is not None else None)
 
         id = self.next_id()
         self._handlers[id] = on_recv