diff --git a/packages/babel-core/src/tools/build-external-helpers.js b/packages/babel-core/src/tools/build-external-helpers.js
index 2b6eba92a1..c6aa2bf6d2 100644
--- a/packages/babel-core/src/tools/build-external-helpers.js
+++ b/packages/babel-core/src/tools/build-external-helpers.js
@@ -3,19 +3,22 @@ import generator from "@babel/generator";
 import template from "@babel/template";
 import * as t from "@babel/types";
 
-const buildUmdWrapper = template(`
-  (function (root, factory) {
-    if (typeof define === "function" && define.amd) {
-      define(AMD_ARGUMENTS, factory);
-    } else if (typeof exports === "object") {
-      factory(COMMON_ARGUMENTS);
-    } else {
-      factory(BROWSER_ARGUMENTS);
-    }
-  })(UMD_ROOT, function (FACTORY_PARAMETERS) {
-    FACTORY_BODY
-  });
-`);
+// Wrapped to avoid wasting time parsing this when almost no-one uses
+// build-external-helpers.
+const buildUmdWrapper = replacements =>
+  template`
+    (function (root, factory) {
+      if (typeof define === "function" && define.amd) {
+        define(AMD_ARGUMENTS, factory);
+      } else if (typeof exports === "object") {
+        factory(COMMON_ARGUMENTS);
+      } else {
+        factory(BROWSER_ARGUMENTS);
+      }
+    })(UMD_ROOT, function (FACTORY_PARAMETERS) {
+      FACTORY_BODY
+    });
+  `(replacements);
 
 function buildGlobal(whitelist) {
   const namespace = t.identifier("babelHelpers");