diff --git a/lib/encoding.js b/lib/encoding.js
index 2ec7414..b5c8904 100644
--- a/lib/encoding.js
+++ b/lib/encoding.js
@@ -6,9 +6,9 @@
  * @fileoverview Global |this| required for resolving indexes in node.
  * @suppress {globalThis}
  */
-if (typeof module !== "undefined" && module.exports) {
-  this["encoding-indexes"] =
-    require("./encoding-indexes.js")["encoding-indexes"];
+if (typeof module !== "undefined" && module.exports &&
+    !this["encoding-indexes"]) {
+    require("./encoding-indexes.js");
 }
 
 (function(global) {