diff --git a/lib/csharp/src/Protocol/TJSONProtocol.cs b/lib/csharp/src/Protocol/TJSONProtocol.cs
index 4081d6e..88d554e 100644
--- a/lib/csharp/src/Protocol/TJSONProtocol.cs
+++ b/lib/csharp/src/Protocol/TJSONProtocol.cs
@@ -505,7 +505,7 @@
         private void WriteJSONDouble(double num)
         {
             context.Write();
-            String str = num.ToString(CultureInfo.InvariantCulture);
+            String str = num.ToString("R", CultureInfo.InvariantCulture);
             bool special = false;
 
             switch (str[0])
diff --git a/lib/csharp/test/ThriftTest/TestClient.cs b/lib/csharp/test/ThriftTest/TestClient.cs
index c09a801..f0297d0 100644
--- a/lib/csharp/test/ThriftTest/TestClient.cs
+++ b/lib/csharp/test/ThriftTest/TestClient.cs
@@ -358,6 +358,14 @@
                 Console.WriteLine("*** FAILED ***");
                 returnCode |= ErrorBaseTypes;
             }
+            Console.Write("testDouble(-0.000341012439638598279)");
+            dub = client.testDouble(-0.000341012439638598279);
+            Console.WriteLine(" = " + dub);
+            if (-0.000341012439638598279 != dub)
+            {
+                Console.WriteLine("*** FAILED ***");
+                returnCode |= ErrorBaseTypes;
+            }
 
             byte[] binOut = PrepareTestData(true);
             Console.Write("testBinary(" + BytesToHex(binOut) + ")");