diff --git a/csharp/src/Google.Protobuf/InvalidJsonException.cs b/csharp/src/Google.Protobuf/InvalidJsonException.cs
new file mode 100644
index 0000000..b543420
--- /dev/null
+++ b/csharp/src/Google.Protobuf/InvalidJsonException.cs
@@ -0,0 +1,53 @@
+#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2015 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using System.IO;
+
+namespace Google.Protobuf
+{
+    /// <summary>
+    /// Thrown when an attempt is made to parse invalid JSON, e.g. using
+    /// a non-string property key, or including a redundant comma. Parsing a protocol buffer
+    /// message represented in JSON using <see cref="JsonParser"/> can throw both this
+    /// exception and <see cref="InvalidProtocolBufferException"/> depending on the situation. This
+    /// exception is only thrown for "pure JSON" errors, whereas <c>InvalidProtocolBufferException</c>
+    /// is thrown when the JSON may be valid in and of itself, but cannot be parsed as a protocol buffer
+    /// message.
+    /// </summary>
+    public sealed class InvalidJsonException : IOException
+    {
+        internal InvalidJsonException(string message)
+            : base(message)
+        {
+        }
+    }
+}
\ No newline at end of file