diff --git a/taskcluster/taskgraph/transforms/tests.py b/taskcluster/taskgraph/transforms/tests.py
index cfb700d493f7..3a3e9f18f239 100644
--- a/taskcluster/taskgraph/transforms/tests.py
+++ b/taskcluster/taskgraph/transforms/tests.py
@@ -1282,6 +1282,7 @@ CHUNK_SUITES_BLACKLIST = (
     'mochitest-a11y',
     'mochitest-browser-chrome',
     'mochitest-browser-chrome-screenshots',
+    'mochitest-browser-chrome-thunderbird',
     'mochitest-chrome',
     'mochitest-devtools-webreplay',
     'mochitest-plain',
@@ -1292,6 +1293,7 @@ CHUNK_SUITES_BLACKLIST = (
     'mochitest-webgl1-ext',
     'mochitest-webgl2-core',
     'mochitest-webgl2-ext',
+    'mozmill',
     'raptor',
     'reftest',
     'reftest-gpu',