diff --git a/pdf.js b/pdf.js
index 68a2597d3..d06d07e0e 100644
--- a/pdf.js
+++ b/pdf.js
@@ -3030,10 +3030,14 @@ var CanvasGraphics = (function() {
             // we want the canvas to be as large as the step size
             var botRight = applyMatrix([x0 + xstep, y0 + ystep], matrix);
 
-            var tmpCanvas = new this.ScratchCanvas(
-                Math.ceil(botRight[0] - topLeft[0]),    // width
-                Math.ceil(botRight[1] - topLeft[1])     // height
-            );
+            var width = botRight[0] - topLeft[0];
+            var height = botRight[1] - topLeft[1];
+
+            // TODO: hack to avoid OOM, remove then pattern code is fixed
+            if (Math.abs(width) > 8192 || Math.abs(height) > 8192)
+                return false;
+
+            var tmpCanvas = new this.ScratchCanvas(width, height);
 
             // set the new canvas element context as the graphics context
             var tmpCtx = tmpCanvas.getContext("2d");
diff --git a/test/test_slave.html b/test/test_slave.html
index 5652a5860..71ec7cacc 100644
--- a/test/test_slave.html
+++ b/test/test_slave.html
@@ -6,7 +6,7 @@
   <script type="text/javascript" src="/fonts.js"></script>
   <script type="text/javascript" src="/glyphlist.js"></script>
   <script type="application/javascript">
-var browser, canvas, currentTask, currentTaskIdx, failure, manifest, pdfDoc, stdout;
+var browser, canvas, currentTask, currentTaskIdx, failure, manifest, numPages, pdfDoc, stdout;
 
 function queryParams() {
     var qs = window.location.search.substring(1);
@@ -66,8 +66,9 @@ function nextTask() {
 
       try {
         pdfDoc = new PDFDoc(new Stream(data));
+        numPages = pdfDoc.numPages;
       } catch(e) {
-        pdfDoc.numPages = 1;
+        numPages = 1;
         failure = 'load PDF doc: '+ e.toString();
       }
 
@@ -78,7 +79,7 @@ function nextTask() {
 }
 
 function nextPage() {
-  if (currentTask.pageNum > pdfDoc.numPages) {
+  if (currentTask.pageNum > numPages) {
     if (++currentTask.round < currentTask.rounds) {
       log("  Round "+ (1 + currentTask.round) +"\n");
       currentTask.pageNum = 1;
@@ -95,8 +96,9 @@ function nextPage() {
   clear(ctx);
 
   var fonts = [];
-  var gfx = new CanvasGraphics(ctx);
+  var gfx = null;
   try {
+    gfx = new CanvasGraphics(ctx);
     currentPage = pdfDoc.getPage(currentTask.pageNum);
     currentPage.compile(gfx, fonts);
   } catch(e) {
@@ -105,9 +107,13 @@ function nextPage() {
 
   var fontLoaderTimer = null;
   function checkFontsLoaded() {
-    if (!FontLoader.bind(fonts)) {
-      fontLoaderTimer = window.setTimeout(checkFontsLoaded, 10);
-      return;
+    try {
+      if (!FontLoader.bind(fonts)) {
+        fontLoaderTimer = window.setTimeout(checkFontsLoaded, 10);
+        return;
+      }
+    } catch(e) {
+      failure = 'fonts: '+ e.toString();
     }
     snapshotCurrentPage(gfx);
   }
@@ -166,7 +172,7 @@ var inFlightRequests = 0;
 function sendTaskResult(snapshot) {
   var result = { browser: browser,
                  id: currentTask.id,
-                 numPages: pdfDoc.numPages,
+                 numPages: numPages,
                  failure: failure,
                  file: currentTask.file,
                  round: currentTask.round,