diff --git a/browser/components/extensions/parent/ext-pkcs11.js b/browser/components/extensions/parent/ext-pkcs11.js
index 334adaa2c3ed1..db6a6af7c87b0 100644
--- a/browser/components/extensions/parent/ext-pkcs11.js
+++ b/browser/components/extensions/parent/ext-pkcs11.js
@@ -7,7 +7,6 @@
 XPCOMUtils.defineLazyModuleGetters(this, {
   ctypes: "resource://gre/modules/ctypes.jsm",
   NativeManifests: "resource://gre/modules/NativeManifests.jsm",
-  OS: "resource://gre/modules/osfile.jsm",
 });
 
 XPCOMUtils.defineLazyServiceGetter(
@@ -17,6 +16,9 @@ XPCOMUtils.defineLazyServiceGetter(
   "nsIPKCS11ModuleDB"
 );
 
+// eslint-disable-next-line mozilla/reject-importGlobalProperties
+Cu.importGlobalProperties(["PathUtils"]);
+
 var { DefaultMap } = ExtensionUtils;
 
 const findModuleByPath = function(path) {
@@ -38,12 +40,18 @@ this.pkcs11 = class extends ExtensionAPI {
       );
       if (hostInfo) {
         if (AppConstants.platform === "win") {
-          hostInfo.manifest.path = OS.Path.join(
-            OS.Path.dirname(hostInfo.path),
-            hostInfo.manifest.path
-          );
+          // If the path specified in the manifest is not an abslute path,
+          // translate it relative to manifest's directory.
+          if (!PathUtils.isAbsolute(hostInfo.manifest.path)) {
+            hostInfo.manifest.path = PathUtils.normalize(
+              PathUtils.joinRelative(
+                PathUtils.parent(hostInfo.path),
+                hostInfo.manifest.path
+              )
+            );
+          }
         }
-        let manifestLib = OS.Path.basename(hostInfo.manifest.path);
+        let manifestLib = PathUtils.filename(hostInfo.manifest.path);
         if (AppConstants.platform !== "linux") {
           manifestLib = manifestLib.toLowerCase(manifestLib);
         }
diff --git a/browser/components/extensions/test/xpcshell/test_ext_pkcs11_management.js b/browser/components/extensions/test/xpcshell/test_ext_pkcs11_management.js
index 6463c5964870d..36f66ecebdece 100644
--- a/browser/components/extensions/test/xpcshell/test_ext_pkcs11_management.js
+++ b/browser/components/extensions/test/xpcshell/test_ext_pkcs11_management.js
@@ -3,28 +3,39 @@
 XPCOMUtils.defineLazyModuleGetters(this, {
   ctypes: "resource://gre/modules/ctypes.jsm",
   MockRegistry: "resource://testing-common/MockRegistry.jsm",
-  OS: "resource://gre/modules/osfile.jsm",
 });
 
 do_get_profile();
-let tmpDir = FileUtils.getDir("TmpD", ["PKCS11"]);
+
+let tmpDir;
+let baseDir;
 let slug =
   AppConstants.platform === "linux" ? "pkcs11-modules" : "PKCS11Modules";
-tmpDir.createUnique(Ci.nsIFile.DIRECTORY_TYPE, FileUtils.PERMS_DIRECTORY);
-let baseDir = OS.Path.join(tmpDir.path, slug);
-OS.File.makeDir(baseDir);
 
-registerCleanupFunction(() => {
-  tmpDir.remove(true);
+add_task(async function setupTest() {
+  tmpDir = await IOUtils.createUniqueDirectory(
+    Services.dirsvc.get("TmpD", Ci.nsIFile).path,
+    "PKCS11"
+  );
+
+  baseDir = PathUtils.join(tmpDir, slug);
+  await IOUtils.makeDirectory(baseDir);
 });
 
-function getPath(filename) {
-  return OS.Path.join(baseDir, filename);
-}
+registerCleanupFunction(async () => {
+  await IOUtils.remove(tmpDir, { recursive: true });
+});
 
-const testmodule =
-  "../../../../../security/manager/ssl/tests/unit/pkcs11testmodule/" +
-  ctypes.libraryName("pkcs11testmodule");
+const testmodule = PathUtils.join(
+  PathUtils.parent(Services.dirsvc.get("CurWorkD", Ci.nsIFile).path, 5),
+  "security",
+  "manager",
+  "ssl",
+  "tests",
+  "unit",
+  "pkcs11testmodule",
+  ctypes.libraryName("pkcs11testmodule")
+);
 
 // This function was inspired by the native messaging test under
 // toolkit/components/extensions
@@ -39,8 +50,8 @@ async function setupManifests(modules) {
       allowed_extensions: [module.id],
     };
 
-    let manifestPath = getPath(`${module.name}.json`);
-    await OS.File.writeAtomic(manifestPath, JSON.stringify(manifest));
+    let manifestPath = PathUtils.join(baseDir, `${module.name}.json`);
+    await IOUtils.writeJSON(manifestPath, manifest);
 
     return manifestPath;
   }
@@ -50,10 +61,11 @@ async function setupManifests(modules) {
     case "linux":
       let dirProvider = {
         getFile(property) {
-          if (property == "XREUserNativeManifests") {
-            return tmpDir.clone();
-          } else if (property == "XRESysNativeManifests") {
-            return tmpDir.clone();
+          if (
+            property == "XREUserNativeManifests" ||
+            property == "XRESysNativeManifests"
+          ) {
+            return new FileUtils.File(tmpDir);
           }
           return null;
         },
@@ -78,10 +90,6 @@ async function setupManifests(modules) {
       });
 
       for (let module of modules) {
-        if (!OS.Path.winIsAbsolute(module.path)) {
-          let cwd = await OS.File.getCurrentDirectory();
-          module.path = OS.Path.join(cwd, module.path);
-        }
         let manifestPath = await writeManifest(module);
         registry.setValue(
           Ci.nsIWindowsRegKey.ROOT_KEY_CURRENT_USER,
@@ -248,13 +256,16 @@ add_task(async function test_pkcs11() {
     {
       name: "internalmodule",
       description: "Builtin Roots Module",
-      path: ctypes.libraryName("nssckbi"),
+      path: PathUtils.join(
+        Services.dirsvc.get("CurWorkD", Ci.nsIFile).path,
+        ctypes.libraryName("nssckbi")
+      ),
       id: "pkcs11@tests.mozilla.org",
     },
     {
       name: "osclientcerts",
       description: "OS Client Cert Module",
-      path: OS.Path.join(libDir.path, ctypes.libraryName("osclientcerts")),
+      path: PathUtils.join(libDir.path, ctypes.libraryName("osclientcerts")),
       id: "pkcs11@tests.mozilla.org",
     },
   ]);