diff --git a/src/MessagePack/MessagePackSerializer.Json.cs b/src/MessagePack/MessagePackSerializer.Json.cs
index 39e9e4113..1dfdf49db 100644
--- a/src/MessagePack/MessagePackSerializer.Json.cs
+++ b/src/MessagePack/MessagePackSerializer.Json.cs
@@ -291,11 +291,11 @@ private static void ToJsonCore(ref MessagePackReader reader, TextWriter writer,
                 case MessagePackType.Float:
                     if (reader.NextCode == MessagePackCode.Float32)
                     {
-                        writer.Write(reader.ReadSingle().ToString(CultureInfo.InvariantCulture));
+                        writer.Write(reader.ReadSingle().ToString("R", CultureInfo.InvariantCulture));
                     }
                     else
                     {
-                        writer.Write(reader.ReadDouble().ToString(CultureInfo.InvariantCulture));
+                        writer.Write(reader.ReadDouble().ToString("R", CultureInfo.InvariantCulture));
                     }
 
                     break;