diff --git a/esinstall/src/rollup-plugins/rollup-plugin-strip-source-mapping.ts b/esinstall/src/rollup-plugins/rollup-plugin-strip-source-mapping.ts
index 42bb480ca8..596354a845 100644
--- a/esinstall/src/rollup-plugins/rollup-plugin-strip-source-mapping.ts
+++ b/esinstall/src/rollup-plugins/rollup-plugin-strip-source-mapping.ts
@@ -9,7 +9,9 @@ export function rollupPluginStripSourceMapping(): Plugin {
   return {
     name: 'snowpack:rollup-plugin-strip-source-mapping',
     transform: (code) => ({
-      code: code.replace(/[^'"`]\/\/+#\s*sourceMappingURL=.+$/gm, ''),
+      code: code
+        // [a-zA-Z0-9-_\*?\.\/\&=+%]: valid URL characters (for sourcemaps)
+        .replace(/\/\/#\s*sourceMappingURL=[a-zA-Z0-9-_\*\?\.\/\&=+%\s]+$/gm, ''),
       map: null,
     }),
   };
diff --git a/test/esinstall/package-es-module-shims/__snapshots__ b/test/esinstall/package-es-module-shims/__snapshots__
new file mode 100644
index 0000000000..a012594453
--- /dev/null
+++ b/test/esinstall/package-es-module-shims/__snapshots__
@@ -0,0 +1,20 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`snowpack install package-es-module-shims: cli output 1`] = `
+"[snowpack] snowpack - A faster build system for the modern web.
+  Snowpack is best configured via config file.
+  But, most configuration can also be passed via CLI flags.
+  📖 https://www.snowpack.dev/#configuration
+Commands:
+  snowpack init         Create a new project config file.
+  snowpack dev          Develop your app locally.
+  snowpack build        Build your app for production.
+  snowpack install      (Advanced) Install web-ready dependencies.
+Flags:
+  --config [path]       Set the location of your project config file.
+  --help                Show this help message.
+  --version             Show the current version.
+  --reload              Clear Snowpack's local cache (troubleshooting).
+  --verbose             View debug info (where available)
+  --quiet               Don’t output anything (dev server will still log minimally)"
+`;
diff --git a/test/rollup-plugins.test.js b/test/rollup-plugins.test.js
new file mode 100644
index 0000000000..8bb0a92f6b
--- /dev/null
+++ b/test/rollup-plugins.test.js
@@ -0,0 +1,49 @@
+const {
+  rollupPluginStripSourceMapping,
+} = require('../esinstall/lib/rollup-plugins/rollup-plugin-strip-source-mapping.js');
+
+describe('snowpack:rollup-plugin-strip-source-mapping', () => {
+  const tests = [
+    {
+      name: 'inline',
+      given: `console.log('foo');//# sourceMappingURL=js.map.js`,
+      expected: `console.log('foo');`,
+    },
+    {
+      name: 'end of file',
+      given: `console.log('foo');
+//# sourceMappingURL=js.map.js`,
+      expected: `console.log('foo');
+`,
+    },
+    {
+      name: 'middle of file',
+      given: `console.log('foo');
+//# sourceMappingURL=js.map.js
+console.log('bar');
+  //# sourceMappingURL=js.map.js`,
+      expected: `console.log('foo');
+
+console.log('bar');
+  `,
+    },
+    {
+      name: 'inside string', // leave alone
+      given: `const myString ='//# sourceMappingURL=js.map.js';`,
+      expected: `const myString ='//# sourceMappingURL=js.map.js';`,
+    },
+    {
+      name: 'es-module-shim', // leave alone
+      given: `    sourceMappingResolved = \`\n//# sourceMappingURL=\` + resolveUrl(sourceMapping.slice(21), load.r);`,
+      expected: `    sourceMappingResolved = \`\n//# sourceMappingURL=\` + resolveUrl(sourceMapping.slice(21), load.r);`,
+    },
+  ];
+
+  const {transform} = rollupPluginStripSourceMapping();
+
+  tests.forEach(({name, given, expected}) => {
+    it(name, () => {
+      expect(transform(given).code).toBe(expected);
+    });
+  });
+});