diff --git a/uriloader/exthandler/tests/unit/xpcshell.ini b/uriloader/exthandler/tests/unit/xpcshell.ini
index 209cfb836a24..57215d1dc5cb 100644
--- a/uriloader/exthandler/tests/unit/xpcshell.ini
+++ b/uriloader/exthandler/tests/unit/xpcshell.ini
@@ -16,6 +16,8 @@ skip-if =
     os == "android"
     appname == "thunderbird"
 [test_filename_sanitize.js]
+skip-if =
+  os == 'mac' # Bug 1817727
 [test_getFromTypeAndExtension.js]
 [test_getMIMEInfo_pdf.js]
 [test_getMIMEInfo_unknown_mime_type.js]