diff --git a/testing/docker/desktop1604-test/Dockerfile b/testing/docker/desktop1604-test/Dockerfile
index 8d83bdec1bff..cc51365f6d76 100644
--- a/testing/docker/desktop1604-test/Dockerfile
+++ b/testing/docker/desktop1604-test/Dockerfile
@@ -10,6 +10,9 @@ ADD topsrcdir/testing/docker/recipes/tooltool.py /setup/tooltool.py
 # %include testing/mozharness/external_tools/robustcheckout.py
 ADD topsrcdir/testing/mozharness/external_tools/robustcheckout.py /usr/local/mercurial/robustcheckout.py
 
+# %include testing/docker/recipes/common.sh
+ADD topsrcdir/testing/docker/recipes/common.sh /setup/common.sh
+
 # %include testing/docker/recipes/install-mercurial.sh
 ADD topsrcdir/testing/docker/recipes/install-mercurial.sh /setup/install-mercurial.sh
 
diff --git a/testing/docker/recipes/common.sh b/testing/docker/recipes/common.sh
new file mode 100644
index 000000000000..ca3fc6996976
--- /dev/null
+++ b/testing/docker/recipes/common.sh
@@ -0,0 +1,10 @@
+#!/bin/bash
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+tooltool_fetch() {
+    cat >manifest.tt
+    python /setup/tooltool.py fetch
+    rm manifest.tt
+}
diff --git a/testing/docker/recipes/ubuntu1604-test-system-setup.sh b/testing/docker/recipes/ubuntu1604-test-system-setup.sh
index 2de028b54d60..12e1a8d5dd88 100644
--- a/testing/docker/recipes/ubuntu1604-test-system-setup.sh
+++ b/testing/docker/recipes/ubuntu1604-test-system-setup.sh
@@ -90,13 +90,7 @@ apt-get install -y -f ${apt_packages[@]}
 
 dpkg-reconfigure locales
 
-# set up tooltool (temporarily)
-tooltool_fetch() {
-    cat >manifest.tt
-    python /setup/tooltool.py fetch
-    rm manifest.tt
-}
-
+. /setup/common.sh
 . /setup/install-mercurial.sh
 
 pip install --upgrade pip