--- a/toolkit/mozapps/extensions/nsBlocklistService.js
+++ b/toolkit/mozapps/extensions/nsBlocklistService.js
@@ -831,16 +831,21 @@ Blocklist.prototype = {
     } else {
       await this._preloadBlocklistFile(BlocklistClients.AddonBlocklistClient.filename);
       await this._preloadBlocklistFile(BlocklistClients.PluginBlocklistClient.filename);
       await this._preloadBlocklistFile(BlocklistClients.GfxBlocklistClient.filename);
     }
   },
 
   async _preloadBlocklistFile(filename) {
+
+    dump(`${FileUtils.getFile(KEY_APPDIR, ['.']).path}  ${FileUtils.getFile(KEY_APPDIR, ['.']).exists()}\n`);
+    dump(`${FileUtils.getFile(KEY_APPDIR, ['defaults']).path}  ${FileUtils.getFile(KEY_APPDIR, ['defaults']).exists()}\n`);
+    dump(`${FileUtils.getFile(KEY_APPDIR, [FILE_BLOCKLIST]).path}, ${FileUtils.getFile(KEY_APPDIR, [FILE_BLOCKLIST]).exists()}\n`);
+
     const {components: filePath} = OS.Path.split(filename);
     let file = FileUtils.getFile(KEY_PROFILEDIR, filePath);
     if (!file.exists()) {
       file = FileUtils.getFile(KEY_APPDIR, filePath);
       if (!file.exists()) {
         file = FileUtils.getFile(KEY_APPDIR, ["defaults"].concat(filePath));
         if (!file.exists()) {
           LOG(`Blocklist::_preloadBlocklistFile: no ${filename} file found`);

--- a/toolkit/mozapps/extensions/test/xpcshell/test_blocklist_json.js
+++ b/toolkit/mozapps/extensions/test/xpcshell/test_blocklist_json.js
@@ -318,20 +318,16 @@ add_task(function* preload_json_reads_pr
   } finally {
     // Clean-up: delete created file.
     clearProfile("addons");
   }
 });
 
 
 add_task(function* load_uses_preloaded_json_if_available() {
-  clearProfile("addons");
-  clearProfile("gfx");
-  clearProfile("plugins");
-
   const blocklist = Blocklist();
 
   // Simulate preload of data.
   const addonsAppPath = FileUtils.getFile(KEY_APPDIR, ["defaults", "blocklists", "addons.json"]).path;
   const gfxAppPath = FileUtils.getFile(KEY_APPDIR, ["defaults", "blocklists", "gfx.json"]).path;
   const pluginsAppPath = FileUtils.getFile(KEY_APPDIR, ["defaults", "blocklists", "plugins.json"]).path;
   blocklist._preloadedBlocklistContent.set(addonsAppPath, JSON.stringify({data: [SAMPLE_ADDON_RECORD]}));
   blocklist._preloadedBlocklistContent.set(gfxAppPath, JSON.stringify({data: [SAMPLE_GFX_RECORD]}));