diff --git a/unit-testing-config-loader.js b/unit-testing-config-loader.js
index cc3e2315..b92fa3a6 100644
--- a/unit-testing-config-loader.js
+++ b/unit-testing-config-loader.js
@@ -6,7 +6,7 @@ module.exports = function ({ appFullPath, projectRoot, angular, rootPagesRegExp
     const testFilesRegExp = /tests\/.*\.(ts|js)/;
     const runnerFullPath = join(projectRoot, "node_modules", "nativescript-unit-test-runner");
     const runnerRelativePath = convertSlashesInPath(relative(appFullPath, runnerFullPath));
-    const appCssFilePath = join(runnerRelativePath, "app.css");
+    const appCssFilePath = convertSlashesInPath(join(runnerRelativePath, "app.css"));
     let source = `
         require("tns-core-modules/bundle-entry-points");
         const runnerContext = require.context("${runnerRelativePath}", true, ${rootPagesRegExp});