exclude actually need to be instance of RegExp

packages/gatsby/src/utils/webpack-utils.ts

@@ -769,26 +769,29 @@ export const createWebpackUtils = (
     }
   ): CssMinimizerPlugin => new CssMinimizerPlugin(options)
 
-  plugins.fastRefresh = ({ modulesThatUseGatsby }): Plugin =>
-    new ReactRefreshWebpackPlugin({
+  plugins.fastRefresh = ({ modulesThatUseGatsby }): Plugin => {
+    const regExpToHack = /node_modules/
+    regExpToHack.test = (modulePath: string): boolean => {
+      // when it's not coming from node_modules we treat it as a source file.
+      if (!vendorRegex.test(modulePath)) {
+        return false
+      }
+
+      // If the module uses Gatsby as a dependency
+      // we want to treat it as src because of shadowing
+      return !modulesThatUseGatsby.some(module =>
+        modulePath.includes(module.path)
+      )
+    }
+
+    return new ReactRefreshWebpackPlugin({
       overlay: false,
       // this is a bit hacky - exclude expect string or regexp or array of those
-      // so this is tricking ReactRefreshWebpackPlugin that we provide RegExp
-      exclude: {
-        test: modulePath => {
-          // when it's not coming from node_modules we treat it as a source file.
-          if (!vendorRegex.test(modulePath)) {
-            return false
-          }
-
-          // If the module uses Gatsby as a dependency
-          // we want to treat it as src because of shadowing
-          return !modulesThatUseGatsby.some(module =>
-            modulePath.includes(module.path)
-          )
-        },
-      } as RegExp,
+      // so this is tricking ReactRefreshWebpackPlugin with providing regexp with
+      // overwritten .test method
+      exclude: regExpToHack,
     })
+  }
 
   plugins.extractText = (options: any): Plugin =>
     new MiniCssExtractPlugin({