diff --git a/src/api.js b/src/api.js
index 32c49c363..bbab680ce 100644
--- a/src/api.js
+++ b/src/api.js
@@ -45,7 +45,7 @@ PDFJS.getDocument = function getDocument(source) {
  * Proxy to a PDFDocument in the worker thread. Also, contains commonly used
  * properties that can be read synchronously.
  */
-var PDFDocumentProxy = (function() {
+var PDFDocumentProxy = (function PDFDocumentProxyClosure() {
   function PDFDocumentProxy(pdfInfo, transport) {
     this.pdfInfo = pdfInfo;
     this.transport = transport;