diff --git a/packages/react-scripts/config/webpack.config.js b/packages/react-scripts/config/webpack.config.js
index 80391927084..746884a03eb 100644
--- a/packages/react-scripts/config/webpack.config.js
+++ b/packages/react-scripts/config/webpack.config.js
@@ -635,8 +635,8 @@ module.exports = function(webpackEnv) {
             '!**/*.json',
             '!**/__tests__/**',
             '!**/?(*.)(spec|test).*',
-            '!src/setupProxy.js',
-            '!src/setupTests.*',
+            '!**/src/setupProxy.*',
+            '!**/src/setupTests.*',
           ],
           watch: paths.appSrc,
           silent: true,
diff --git a/packages/react-scripts/scripts/utils/createJestConfig.js b/packages/react-scripts/scripts/utils/createJestConfig.js
index abfd92c8d3c..58c2ad48812 100644
--- a/packages/react-scripts/scripts/utils/createJestConfig.js
+++ b/packages/react-scripts/scripts/utils/createJestConfig.js
@@ -14,15 +14,13 @@ const paths = require('../../config/paths');
 module.exports = (resolve, rootDir, isEjecting) => {
   // Use this instead of `paths.testsSetup` to avoid putting
   // an absolute filename into configuration after ejecting.
-  const setupTestsMatches = paths.testsSetup.match(/src\/setupTests\.(.+)/);
+  const setupTestsMatches = paths.testsSetup.match(/src[/\\]setupTests\.(.+)/);
   const setupTestsFileExtension =
     (setupTestsMatches && setupTestsMatches[1]) || 'js';
   const setupTestsFile = fs.existsSync(paths.testsSetup)
     ? `<rootDir>/src/setupTests.${setupTestsFileExtension}`
     : undefined;
 
-  // TODO: I don't know if it's safe or not to just use / as path separator
-  // in Jest configs. We need help from somebody with Windows to determine this.
   const config = {
     collectCoverageFrom: ['src/**/*.{js,jsx,ts,tsx}', '!src/**/*.d.ts'],