diff --git a/pdf.js b/pdf.js
index 378c17580..440385563 100644
--- a/pdf.js
+++ b/pdf.js
@@ -5649,8 +5649,9 @@ var CanvasGraphics = (function canvasGraphics() {
       var tmpCtx = tmpCanvas.getContext('2d');
       if (imageObj.imageMask) {
         var fillColor = this.current.fillColor;
-        tmpCtx.fillStyle = (fillColor && fillColor.type === 'Pattern') ?
-          fillColor.getPattern(tmpCtx) : fillColor;
+        tmpCtx.fillStyle = (fillColor && fillColor.hasOwnProperty('type') &&
+                            fillColor.type === 'Pattern') ?
+                            fillColor.getPattern(tmpCtx) : fillColor;
         tmpCtx.fillRect(0, 0, w, h);
       }
       var imgData = tmpCtx.getImageData(0, 0, w, h);