diff --git a/CHANGELOG.md b/CHANGELOG.md
index 10f2921..3e279ea 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+## 2.0.5
+
+* Changed the max message size instead to 0x3ffffffffffff, which is the largest
+  portable value for both JS and the Dart VM.
+
 ## 2.0.4
 
 * Made max message size a BigNum instead of an int so that dart2js can compile
diff --git a/lib/src/hash_sink.dart b/lib/src/hash_sink.dart
index 592dd22..fde6b08 100644
--- a/lib/src/hash_sink.dart
+++ b/lib/src/hash_sink.dart
@@ -26,6 +26,11 @@
   /// used across invocations of [_iterate].
   final Uint32List _currentChunk;
 
+  /// Messages with more than 2^53-1 bits are not supported. (This is the
+  /// largest value that is representable on both JS and the Dart VM.)
+  /// So the maximum length in bytes is (2^53-1)/8.
+  static const _maxMessageLengthInBytes = 0x0003ffffffffffff;
+
   /// The length of the input data so far, in bytes.
   int _lengthInBytes = 0;
 
@@ -121,12 +126,9 @@
       _pendingData.add(0);
     }
 
-    if (new BigInt.from(_lengthInBytes) >
-        (new BigInt.from(2).pow(64) - BigInt.one)) {
-      // Messages with more than 2^64-1 bits are not supported.
-      // So the maximum length in bytes is (2^64-1)/8.
+    if (_lengthInBytes > _maxMessageLengthInBytes) {
       throw new UnsupportedError(
-          'Hashing is unsupported for messages with more than 2^64 bits.');
+          'Hashing is unsupported for messages with more than 2^53 bits.');
     }
 
     var lengthInBits = _lengthInBytes * bitsPerByte;
diff --git a/pubspec.yaml b/pubspec.yaml
index 085f972..ff8f0aa 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: crypto
-version: 2.0.4
+version: 2.0.5
 author: Dart Team <misc@dartlang.org>
 description: Library of cryptographic functions.
 homepage: https://www.github.com/dart-lang/crypto