--- a/devtools/server/actors/inspector.js
+++ b/devtools/server/actors/inspector.js
@@ -3025,18 +3025,19 @@ var imageToImageData = Task.async(functi
   let imgMax = Math.max(imgWidth, imgHeight);
   if (maxDim && imgMax > maxDim) {
     resizeRatio = maxDim / imgMax;
   }
 
   // Extract the image data
   let imageData;
   // The image may already be a data-uri, in which case, save ourselves the
-  // trouble of converting via the canvas.drawImage.toDataURL method
-  if (isImg && node.src.startsWith("data:")) {
+  // trouble of converting via the canvas.drawImage.toDataURL method, but only
+  // if the image doesn't need resizing
+  if (isImg && node.src.startsWith("data:") && resizeRatio === 1) {
     imageData = node.src;
   } else {
     // Create a canvas to copy the rawNode into and get the imageData from
     let canvas = node.ownerDocument.createElementNS(XHTML_NS, "canvas");
     canvas.width = imgWidth * resizeRatio;
     canvas.height = imgHeight * resizeRatio;
     let ctx = canvas.getContext("2d");