diff --git a/Merlin/Main/Languages/Ruby/Libraries.LCA_RESTRICTED/Builtins/IoOps.cs b/Merlin/Main/Languages/Ruby/Libraries.LCA_RESTRICTED/Builtins/IoOps.cs
index 6da6a3d..a22adbe 100644
--- a/Merlin/Main/Languages/Ruby/Libraries.LCA_RESTRICTED/Builtins/IoOps.cs
+++ b/Merlin/Main/Languages/Ruby/Libraries.LCA_RESTRICTED/Builtins/IoOps.cs
@@ -16,6 +16,7 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.Globalization;
 using System.IO;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
@@ -628,7 +629,7 @@ namespace IronRuby.Builtins {
             } else if (obj is bool) {
                 return MutableString.Create((bool)obj ? "true" : "false");
             } else if (obj is double) {
-                var result = MutableString.Create(obj.ToString());
+                var result = MutableString.Create(Convert.ToString(obj, CultureInfo.InvariantCulture));
                 if ((double)(int)(double)obj == (double)obj) {
                     result.Append(".0");
                 }