diff --git a/src/stream.js b/src/stream.js
index 1067e42c7..4a9c1dabe 100644
--- a/src/stream.js
+++ b/src/stream.js
@@ -1201,66 +1201,53 @@ var AsciiHexStream = (function AsciiHexStreamClosure() {
     this.str = str;
     this.dict = str.dict;
 
+    this.firstDigit = -1;
+
     DecodeStream.call(this);
   }
 
-  var hexvalueMap = {
-      9: -1, // \t
-      32: -1, // space
-      48: 0,
-      49: 1,
-      50: 2,
-      51: 3,
-      52: 4,
-      53: 5,
-      54: 6,
-      55: 7,
-      56: 8,
-      57: 9,
-      65: 10,
-      66: 11,
-      67: 12,
-      68: 13,
-      69: 14,
-      70: 15,
-      97: 10,
-      98: 11,
-      99: 12,
-      100: 13,
-      101: 14,
-      102: 15
-  };
-
   AsciiHexStream.prototype = Object.create(DecodeStream.prototype);
 
   AsciiHexStream.prototype.readBlock = function AsciiHexStream_readBlock() {
-    var gtCode = '>'.charCodeAt(0), bytes = this.str.getBytes(), c, n,
-        decodeLength, buffer, bufferLength, i, length;
-
-    decodeLength = (bytes.length + 1) >> 1;
-    buffer = this.ensureBuffer(this.bufferLength + decodeLength);
-    bufferLength = this.bufferLength;
-
-    for (i = 0, length = bytes.length; i < length; i++) {
-      c = hexvalueMap[bytes[i]];
-      while (c == -1 && (i + 1) < length) {
-        c = hexvalueMap[bytes[++i]];
-      }
-
-      if ((i + 1) < length && (bytes[i + 1] !== gtCode)) {
-        n = hexvalueMap[bytes[++i]];
-        buffer[bufferLength++] = c * 16 + n;
-      } else {
-        // EOD marker at an odd number, behave as if a 0 followed the last
-        // digit.
-        if (bytes[i] !== gtCode) {
-          buffer[bufferLength++] = c * 16;
-        }
-      }
+    var UPSTREAM_BLOCK_SIZE = 8000;
+    var bytes = this.str.getBytes(UPSTREAM_BLOCK_SIZE);
+    if (!bytes.length) {
+      this.eof = true;
+      return;
     }
 
+    var maxDecodeLength = (bytes.length + 1) >> 1;
+    var buffer = this.ensureBuffer(this.bufferLength + maxDecodeLength);
+    var bufferLength = this.bufferLength;
+
+    var firstDigit = this.firstDigit;
+    for (var i = 0, ii = bytes.length; i < ii; i++) {
+      var ch = bytes[i], digit;
+      if (ch >= 0x30 && ch <= 0x39) { // '0'-'9'
+        digit = ch & 0x0F;
+      } else if ((ch >= 0x41 && ch <= 0x46) || (ch >= 0x61 && ch <= 0x66)) {
+        // 'A'-'Z', 'a'-'z'
+        digit = (ch & 0x0F) + 9;
+      } else if (ch === 0x3E) { // '>'
+        this.eof = true;
+        break;
+      } else { // probably whitespace
+        continue; // ignoring
+      }
+      if (firstDigit < 0) {
+        firstDigit = digit;
+      } else {
+        buffer[bufferLength++] = (firstDigit << 4) | digit;
+        firstDigit = -1;
+      }
+    }
+    if (firstDigit >= 0 && this.eof) {
+      // incomplete byte
+      buffer[bufferLength++] = (firstDigit << 4);
+      firstDigit = -1;
+    }
+    this.firstDigit = firstDigit;
     this.bufferLength = bufferLength;
-    this.eof = true;
   };
 
   return AsciiHexStream;
diff --git a/test/pdfs/bug889327.pdf.link b/test/pdfs/bug889327.pdf.link
new file mode 100644
index 000000000..4590a69a7
--- /dev/null
+++ b/test/pdfs/bug889327.pdf.link
@@ -0,0 +1 @@
+https://bugzilla.mozilla.org/attachment.cgi?id=770134
diff --git a/test/test_manifest.json b/test/test_manifest.json
index 97d622650..836c826ff 100644
--- a/test/test_manifest.json
+++ b/test/test_manifest.json
@@ -1252,6 +1252,14 @@
       "rounds": 1,
       "type": "eq"
     },
+    {  "id": "bug889327",
+      "file": "pdfs/bug889327.pdf",
+      "md5": "b45cd63419241c40731f98d0e1dac082",
+      "link": true,
+      "lastPage": 1,
+      "rounds": 1,
+      "type": "eq"
+    },
     {  "id": "issue2829",
       "file": "pdfs/issue2829.pdf",
       "md5": "f32b28cf8792f6ccc470446bfbb38584",