diff --git a/python/mozbuild/mozbuild/backend/recursivemake.py b/python/mozbuild/mozbuild/backend/recursivemake.py
index 2138e593bad5..c64e73914ccd 100644
--- a/python/mozbuild/mozbuild/backend/recursivemake.py
+++ b/python/mozbuild/mozbuild/backend/recursivemake.py
@@ -135,6 +135,7 @@ DEPRECATED_VARIABLES = [
     'MOCHITEST_FILES_PARTS',
     'MOCHITEST_METRO_FILES',
     'MOCHITEST_ROBOCOP_FILES',
+    'MOZ_CHROME_FILE_FORMAT',
     'SHORT_LIBNAME',
     'TESTING_JS_MODULES',
     'TESTING_JS_MODULE_DIR',
diff --git a/testing/mochitest/Makefile.in b/testing/mochitest/Makefile.in
index 7f30eab97a49..dbba13a599b0 100644
--- a/testing/mochitest/Makefile.in
+++ b/testing/mochitest/Makefile.in
@@ -3,7 +3,6 @@
 # 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/.
 
-MOZ_CHROME_FILE_FORMAT = jar
 
 _DEST_DIR = $(DEPTH)/_tests/$(relativesrcdir)
 
diff --git a/testing/specialpowers/Makefile.in b/testing/specialpowers/Makefile.in
index bc041636c2db..b20132f62ba6 100644
--- a/testing/specialpowers/Makefile.in
+++ b/testing/specialpowers/Makefile.in
@@ -3,7 +3,6 @@
 # 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/.
 
-MOZ_CHROME_FILE_FORMAT = flat
 
 TEST_EXTENSIONS_DIR = $(DEPTH)/testing/specialpowers