--- a/toolkit/components/extensions/test/mochitest/mochitest-common.ini
+++ b/toolkit/components/extensions/test/mochitest/mochitest-common.ini
@@ -81,17 +81,16 @@ skip-if = os == 'android' # bug 1369440
 skip-if = os == 'android' && debug # The generated script takes too long to load on Android debug
 [test_ext_contentscript_cache.html]
 skip-if = (os == 'linux' && debug) || (toolkit == 'android' && debug) # bug 1348241
 [test_ext_contentscript_canvas.html]
 [test_ext_contentscript_context.html]
 [test_ext_contentscript_create_iframe.html]
 [test_ext_contentscript_css.html]
 [test_ext_contentscript_devtools_metadata.html]
-skip-if = os == 'win' # bug 1434777
 [test_ext_contentscript_exporthelpers.html]
 [test_ext_contentscript_incognito.html]
 skip-if = os == 'android' # Android does not support multiple windows.
 [test_ext_contentscript_permission.html]
 [test_ext_contentscript_teardown.html]
 [test_ext_cookies.html]
 [test_ext_cookies_containers.html]
 [test_ext_cookies_expiry.html]