diff --git a/lib/parser/utils.js b/lib/parser/utils.js
index 51270b6c..4a23ea5b 100644
--- a/lib/parser/utils.js
+++ b/lib/parser/utils.js
@@ -10,19 +10,21 @@ function normalizedFunctionString(fn) {
   return fn.toString().replace('function(', 'function (');
 }
 
-let randomBytes;
-if (typeof window !== 'undefined') {
-  if (window.crypto && window.crypto.getRandomValues) {
-    randomBytes = size => window.crypto.getRandomValues(new Uint8Array(size));
-  } else {
-    randomBytes = size => {
-      const result = new Uint8Array(size);
-      for (let i = 0; i < size; ++i) result[i] = Math.floor(Math.random() * 256);
-      return result;
-    };
-  }
+function insecureRandomBytes(size) {
+  const result = new Uint8Array(size);
+  for (let i = 0; i < size; ++i) result[i] = Math.floor(Math.random() * 256);
+  return result;
+}
+
+let randomBytes = insecureRandomBytes;
+if (typeof window !== 'undefined' && window.crypto && window.crypto.getRandomValues) {
+  randomBytes = size => window.crypto.getRandomValues(new Uint8Array(size));
 } else {
-  randomBytes = require('crypto').randomBytes;
+  try {
+    randomBytes = require('crypto').randomBytes;
+  } catch (e) {
+    // keep the fallback
+  }
 }
 
 module.exports = {