diff --git a/dom/imptests/Makefile.in b/dom/imptests/Makefile.in
deleted file mode 100644
index 397ab02d445..00000000000
--- a/dom/imptests/Makefile.in
+++ /dev/null
@@ -1,14 +0,0 @@
-# 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/.
-
-SUPPORT_FILES = \
-  testharness.js \
-  testharnessreport.js \
-  testharness.css \
-  idlharness.js \
-  WebIDLParser.js \
-  $(NULL)
-
-SUPPORT_DEST = $(DEPTH)/_tests/testing/mochitest/resources
-INSTALL_TARGETS += SUPPORT
diff --git a/dom/imptests/mochitest.ini b/dom/imptests/mochitest.ini
new file mode 100644
index 00000000000..b3659e25b72
--- /dev/null
+++ b/dom/imptests/mochitest.ini
@@ -0,0 +1,7 @@
+[DEFAULT]
+support-files =
+  /resources/testharness.js
+  /resources/testharnessreport.js
+  /resources/testharness.css
+  /resources/idlharness.js
+  /resources/WebIDLParser.js
diff --git a/dom/imptests/moz.build b/dom/imptests/moz.build
index fad48998e84..0182e15da0a 100644
--- a/dom/imptests/moz.build
+++ b/dom/imptests/moz.build
@@ -7,6 +7,7 @@
 MOCHITEST_MANIFESTS += [
     'editing/mochitest.ini',
     'html/mochitest.ini',
+    'mochitest.ini',
     'webapps/mochitest.ini',
 ]