diff --git a/examples/custom-generator-codelab/webpack.config.js b/examples/custom-generator-codelab/webpack.config.js
index 2a34f99c6c..1a095648fd 100644
--- a/examples/custom-generator-codelab/webpack.config.js
+++ b/examples/custom-generator-codelab/webpack.config.js
@@ -46,14 +46,14 @@ module.exports = (env, argv) => {
 
     // Include the source maps for Blockly for easier debugging Blockly code.
     config.module.rules.push({
-      test: /(blockly\/.*\.js)$/,
+      test: /(blockly[/\\].*\.js)$/,
       use: [require.resolve('source-map-loader')],
       enforce: 'pre',
     });
 
     // Ignore spurious warnings from source-map-loader
     // It can't find source maps for some Closure modules and that is expected
-    config.ignoreWarnings = [/Failed to parse source map/];
+    config.ignoreWarnings = [/Failed to parse source map.*blockly/];
   }
   return config;
 };
diff --git a/examples/custom-renderer-codelab/webpack.config.js b/examples/custom-renderer-codelab/webpack.config.js
index 2a34f99c6c..1a095648fd 100644
--- a/examples/custom-renderer-codelab/webpack.config.js
+++ b/examples/custom-renderer-codelab/webpack.config.js
@@ -46,14 +46,14 @@ module.exports = (env, argv) => {
 
     // Include the source maps for Blockly for easier debugging Blockly code.
     config.module.rules.push({
-      test: /(blockly\/.*\.js)$/,
+      test: /(blockly[/\\].*\.js)$/,
       use: [require.resolve('source-map-loader')],
       enforce: 'pre',
     });
 
     // Ignore spurious warnings from source-map-loader
     // It can't find source maps for some Closure modules and that is expected
-    config.ignoreWarnings = [/Failed to parse source map/];
+    config.ignoreWarnings = [/Failed to parse source map.*blockly/];
   }
   return config;
 };
diff --git a/examples/keyboard-navigation-codelab/webpack.config.js b/examples/keyboard-navigation-codelab/webpack.config.js
index 2a34f99c6c..1a095648fd 100644
--- a/examples/keyboard-navigation-codelab/webpack.config.js
+++ b/examples/keyboard-navigation-codelab/webpack.config.js
@@ -46,14 +46,14 @@ module.exports = (env, argv) => {
 
     // Include the source maps for Blockly for easier debugging Blockly code.
     config.module.rules.push({
-      test: /(blockly\/.*\.js)$/,
+      test: /(blockly[/\\].*\.js)$/,
       use: [require.resolve('source-map-loader')],
       enforce: 'pre',
     });
 
     // Ignore spurious warnings from source-map-loader
     // It can't find source maps for some Closure modules and that is expected
-    config.ignoreWarnings = [/Failed to parse source map/];
+    config.ignoreWarnings = [/Failed to parse source map.*blockly/];
   }
   return config;
 };
diff --git a/examples/sample-app-ts/webpack.config.js b/examples/sample-app-ts/webpack.config.js
index 02a02544d0..da23023d80 100644
--- a/examples/sample-app-ts/webpack.config.js
+++ b/examples/sample-app-ts/webpack.config.js
@@ -54,14 +54,14 @@ module.exports = (env, argv) => {
 
     // Include the source maps for Blockly for easier debugging Blockly code.
     config.module.rules.push({
-      test: /(blockly\/.*\.js)$/,
+      test: /(blockly[/\\].*\.js)$/,
       use: [require.resolve('source-map-loader')],
       enforce: 'pre',
     });
 
     // Ignore spurious warnings from source-map-loader
     // It can't find source maps for some Closure modules and that is expected
-    config.ignoreWarnings = [/Failed to parse source map/];
+    config.ignoreWarnings = [/Failed to parse source map.*blockly/];
   }
   return config;
 };
diff --git a/examples/sample-app/webpack.config.js b/examples/sample-app/webpack.config.js
index 2a34f99c6c..1a095648fd 100644
--- a/examples/sample-app/webpack.config.js
+++ b/examples/sample-app/webpack.config.js
@@ -46,14 +46,14 @@ module.exports = (env, argv) => {
 
     // Include the source maps for Blockly for easier debugging Blockly code.
     config.module.rules.push({
-      test: /(blockly\/.*\.js)$/,
+      test: /(blockly[/\\].*\.js)$/,
       use: [require.resolve('source-map-loader')],
       enforce: 'pre',
     });
 
     // Ignore spurious warnings from source-map-loader
     // It can't find source maps for some Closure modules and that is expected
-    config.ignoreWarnings = [/Failed to parse source map/];
+    config.ignoreWarnings = [/Failed to parse source map.*blockly/];
   }
   return config;
 };
diff --git a/plugins/dev-scripts/config/webpack.config.js b/plugins/dev-scripts/config/webpack.config.js
index 9da8a53735..2f3c82e93f 100644
--- a/plugins/dev-scripts/config/webpack.config.js
+++ b/plugins/dev-scripts/config/webpack.config.js
@@ -107,7 +107,7 @@ module.exports = (env) => {
       rules: [
         // Load Blockly source maps.
         {
-          test: /(blockly\/.*\.js)$/,
+          test: /(blockly[/\\].*\.js)$/,
           use: [require.resolve('source-map-loader')],
           enforce: 'pre',
         },
@@ -119,7 +119,7 @@ module.exports = (env) => {
     },
     // Ignore spurious warnings from source-map-loader
     // It can't find source maps for some Closure modules and that is expected
-    ignoreWarnings: [/Failed to parse source map/],
+    ignoreWarnings: [/Failed to parse source map.*blockly/],
     plugins,
     externals: isProduction
       ? {