diff --git a/Makefile b/Makefile
index 3e385b175..2cc886091 100644
--- a/Makefile
+++ b/Makefile
@@ -63,6 +63,7 @@ bundle: | $(BUILD_DIR)
 	@cd src; \
 	cat $(PDF_JS_FILES) > all_files.tmp; \
 	sed '/PDFJSSCRIPT_INCLUDE_ALL/ r all_files.tmp' pdf.js > ../$(BUILD_TARGET); \
+	sed -i '' "s/PDFJSSCRIPT_BUNDLE_VER/`git log --format="%H" -n 1`/" ../$(BUILD_TARGET); \
 	rm -f *.tmp; \
 	cd ..
 
diff --git a/src/pdf.js b/src/pdf.js
index 51f606548..1a551d300 100644
--- a/src/pdf.js
+++ b/src/pdf.js
@@ -7,8 +7,9 @@ var PDFJS = {};
   // Use strict in our context only - users might not want it
   'use strict';
 
+  PDFJS.build = "PDFJSSCRIPT_BUNDLE_VER";
+
   // Files are inserted below - see Makefile
   /* PDFJSSCRIPT_INCLUDE_ALL */
 
 }).call((typeof window === 'undefined') ? this : window);
-