diff --git a/firefox-mochitest.patch b/firefox-mochitest.patch
new file mode 100644
index 0000000..c7539be
--- /dev/null
+++ b/firefox-mochitest.patch
@@ -0,0 +1,9 @@
+diff --git a/testing/tools/websocketprocessbridge/websocketprocessbridge_requirements_3.txt b/testing/tools/websocketprocessbridge/websocketprocessbridge_requirements_3.txt
+--- a/testing/tools/websocketprocessbridge/websocketprocessbridge_requirements_3.txt
++++ b/testing/tools/websocketprocessbridge/websocketprocessbridge_requirements_3.txt
+@@ -1,4 +1,5 @@
+ # This file is the websocketprocess requirements.txt used with python 3.
++pyrsistent
+ 
+ # needed by txws, and we'd like pip to get it from the local server before setuptools tries pypi
+ six