diff --git a/js/lib/cs_widget.js b/js/lib/cs_widget.js
index f1b61a7..b82a779 100644
--- a/js/lib/cs_widget.js
+++ b/js/lib/cs_widget.js
@@ -3,9 +3,11 @@ var _ = require('lodash');
 var cs = require('cornerstone-core');
 var cm = require('cornerstone-math');
 var ctools = require('cornerstone-tools');
+var hammerjs = require('hammerjs');
 
 ctools.external.cornerstone = cs;
 ctools.external.cornerstoneMath = cm;
+ctools.external.Hammer = hammerjs.Hammer;
 
 // When serialiazing the entire widget state for embedding, only values that
 // differ from the defaults will be specified.
diff --git a/js/package.json b/js/package.json
index b8668b0..1f0ff7a 100644
--- a/js/package.json
+++ b/js/package.json
@@ -32,7 +32,8 @@
     "@jupyter-widgets/base": "^1.0.0",
     "cornerstone-core": "^2.2.4",
     "cornerstone-math": "^0.1.6",
-    "cornerstone-tools": "^2.3.9"
+    "cornerstone-tools": "^2.3.9",
+    "hammerjs": "2.0.8"
   },
   "jupyterlab": {
     "extension": "lib/labplugin"