diff --git a/src/display/canvas.js b/src/display/canvas.js
index fe6fedd10..4e55d0271 100644
--- a/src/display/canvas.js
+++ b/src/display/canvas.js
@@ -1099,12 +1099,7 @@ var CanvasGraphics = (function CanvasGraphicsClosure() {
           ctx.fill();
           ctx.mozFillRule = 'nonzero';
         } else {
-          try {
-            ctx.fill('evenodd');
-          } catch (ex) {
-            // shouldn't really happen, but browsers might think differently
-            ctx.fill();
-          }
+          ctx.fill('evenodd');
         }
         this.pendingEOFill = false;
       } else {
@@ -2117,12 +2112,7 @@ var CanvasGraphics = (function CanvasGraphicsClosure() {
             ctx.clip();
             ctx.mozFillRule = 'nonzero';
           } else {
-            try {
-              ctx.clip('evenodd');
-            } catch (ex) {
-              // shouldn't really happen, but browsers might think differently
-              ctx.clip();
-            }
+            ctx.clip('evenodd');
           }
         } else {
           ctx.clip();
diff --git a/web/compatibility.js b/web/compatibility.js
index 06f54bff0..6d91057f1 100644
--- a/web/compatibility.js
+++ b/web/compatibility.js
@@ -522,9 +522,9 @@ if (typeof PDFJS === 'undefined') {
 
     if (polyfill) {
       var contextPrototype = window.CanvasRenderingContext2D.prototype;
-      contextPrototype._createImageData = contextPrototype.createImageData;
+      var createImageData = contextPrototype.createImageData;
       contextPrototype.createImageData = function(w, h) {
-        var imageData = this._createImageData(w, h);
+        var imageData = createImageData.call(this, w, h);
         imageData.data.set = function(arr) {
           for (var i = 0, ii = this.length; i < ii; i++) {
             this[i] = arr[i];
@@ -532,6 +532,8 @@ if (typeof PDFJS === 'undefined') {
         };
         return imageData;
       };
+      // this closure will be kept referenced, so clear its vars
+      contextPrototype = null;
     }
   }
 })();