diff --git a/mx-tester.yml b/mx-tester.yml
index ca34105..5e7d471 100644
--- a/mx-tester.yml
+++ b/mx-tester.yml
@@ -4,6 +4,11 @@ up:
   before:
     # Launch the reverse proxy, listening for connections *only* on the local host.
     - docker run --rm --network host --name mjolnir-test-reverse-proxy -p 127.0.0.1:8081:80 -v $MX_TEST_CWD/test/nginx.conf:/etc/nginx/nginx.conf:ro -d nginx
+  after:
+    # Wait until Synapse is ready
+    - until curl localhost:9999 --stderr /dev/null > /dev/null; do echo "Waiting for Synapse..."; sleep 1s; done
+    - echo "Synapse is ready"
+
 run:
   - yarn test:integration
 down: