diff --git a/lib/cypress-plugin/modifySpec.js b/lib/cypress-plugin/modifySpec.js
index abe03ac..b0e4bae 100644
--- a/lib/cypress-plugin/modifySpec.js
+++ b/lib/cypress-plugin/modifySpec.js
@@ -22,6 +22,13 @@ const path = require('path');
  * @returns {String} - New spec file with added before block
  */
 module.exports = (fileContents, version, source, target) => {
+  const re = /(?:\.([^.]+))?$/;
+
+  // Only parse the following files.
+  if (!['js', 'jsx', 'ts', 'tsx'].includes(re.exec(source)[0])) {
+    return fileContents;
+  }
+
   const beforeBlock = esprima.parseScript(`
     before(() => {
       const path = require('path');