diff --git a/taskcluster/ci/test/mochitest.yml b/taskcluster/ci/test/mochitest.yml
index 0a62a1a2cd4169f2190679d7704bf08024cae008..dd5d08c79d6ca32d8d740ee75886cb1040fb640b 100644
--- a/taskcluster/ci/test/mochitest.yml
+++ b/taskcluster/ci/test/mochitest.yml
@@ -293,7 +293,7 @@ mochitest-browser-chrome:
     # Bug 1281241: migrating to m3.large instances
     instance-size:
         by-test-platform:
-            linux.*64-tsan-qr/opt: xlarge  # runs out of memory using 8GB
+            linux.*64-tsan-qr/opt: xlarge-noscratch  # runs out of memory using 8GB
             default: default
     allow-software-gl-layers: false