diff --git a/external/jpgjs/jpg.js b/external/jpgjs/jpg.js
index 6873fc6c3..b5f0c95f3 100644
--- a/external/jpgjs/jpg.js
+++ b/external/jpgjs/jpg.js
@@ -668,9 +668,11 @@ var JpegImage = (function jpegImage() {
             break;
 
           case 0xFFC0: // SOF0 (Start of Frame, Baseline DCT)
+          case 0xFFC1: // SOF1 (Start of Frame, Extended DCT)
           case 0xFFC2: // SOF2 (Start of Frame, Progressive DCT)
             readUint16(); // skip data length
             frame = {};
+            frame.extended = (fileMarker === 0xFFC1);
             frame.progressive = (fileMarker === 0xFFC2);
             frame.precision = data[offset++];
             frame.scanLines = readUint16();
@@ -792,6 +794,21 @@ var JpegImage = (function jpegImage() {
             }
           }
           break;
+        case 2:
+          // PDF might compress two component data in custom colorspace
+          component1 = this.components[0];
+          component2 = this.components[1];
+          for (y = 0; y < height; y++) {
+            component1Line = component1.lines[0 | (y * component1.scaleY * scaleY)];
+            component2Line = component1.lines[0 | (y * component2.scaleY * scaleY)];
+            for (x = 0; x < width; x++) {
+              Y = component1Line[0 | (x * component1.scaleX * scaleX)];
+              data[offset++] = Y;
+              Y = component2Line[0 | (x * component2.scaleX * scaleX)];
+              data[offset++] = Y;
+            }
+          }
+          break;
         case 3:
           // The default transform for three components is true
           colorTransform = true;
diff --git a/test/pdfs/bug766138.pdf.link b/test/pdfs/bug766138.pdf.link
new file mode 100644
index 000000000..68402dbde
--- /dev/null
+++ b/test/pdfs/bug766138.pdf.link
@@ -0,0 +1 @@
+http://www.minneapolismn.gov/www/groups/public/@clerk/documents/webcontent/wcms1p-094235.pdf
diff --git a/test/test_manifest.json b/test/test_manifest.json
index ad46feba8..9f4236fbe 100644
--- a/test/test_manifest.json
+++ b/test/test_manifest.json
@@ -1201,6 +1201,13 @@
       "rounds": 1,
       "type": "eq"
     },
+    {  "id": "bug766138",
+      "file": "pdfs/bug766138.pdf",
+      "md5": "b171f5cf8d9834348112fba60ee54f8c",
+      "link": true,
+      "rounds": 1,
+      "type": "eq"
+    },
     {  "id": "issue2829",
       "file": "pdfs/issue2829.pdf",
       "md5": "f32b28cf8792f6ccc470446bfbb38584",