diff --git a/Tests/Kernels/Cosmos.Compiler.Tests.Bcl.System/System/UInt64Test.cs b/Tests/Kernels/Cosmos.Compiler.Tests.Bcl.System/System/UInt64Test.cs
index de0900af2..3b90380bc 100644
--- a/Tests/Kernels/Cosmos.Compiler.Tests.Bcl.System/System/UInt64Test.cs
+++ b/Tests/Kernels/Cosmos.Compiler.Tests.Bcl.System/System/UInt64Test.cs
@@ -18,6 +18,8 @@ namespace Cosmos.Compiler.Tests.Bcl.System
             expectedResult = "18446744073709551615";
 
             Assert.IsTrue((result == expectedResult), "UInt64.ToString doesn't work");
+            Assert.IsTrue(value.ToString("X") == "FFFFFFFFFFFFFFFF", "UInt64.ToString(X) doesn't work");
+            Assert.IsTrue(((ulong)0x121411443).ToString("X") == "121411443", "UInt64.ToString(X) doesn't work");
 
             // Now let's try to concat to a String using '+' operator
             result = "The Maximum value of an UInt64 is " + value;
diff --git a/source/Cosmos.Common/Extensions/ToHexString.cs b/source/Cosmos.Common/Extensions/ToHexString.cs
index 9703d1d9f..26a416309 100644
--- a/source/Cosmos.Common/Extensions/ToHexString.cs
+++ b/source/Cosmos.Common/Extensions/ToHexString.cs
@@ -112,13 +112,22 @@
         }
 
         /// <summary>
-        /// Convert 64-bit unsigned int to 16 characters long hexadecimal string, padded with '0's.
+        /// Convert 64-bit unsigned int to 16 characters long hexadecimal string, optionally padded with '0's.
         /// </summary>
         /// <param name="aValue">A 64-bit unsigned int to be converted to hexadecimal string.</param>
-        /// <returns>16 characters long string value, padded with '0's.</returns>
-        public static string ToHex(this ulong aValue)
+        /// <param name="withPadding">Determines if a left padding should be applied</param>
+        /// <returns>16 characters long string value, optionally padded with '0's.</returns>
+        public static string ToHex(this ulong aValue, bool withPadding = true)
         {
-            return ConvertToHex(aValue).PadLeft(16, '0');
+            var hex = ConvertToHex(aValue);
+            if (withPadding)
+            {
+                return hex.PadLeft(16, '0');
+            }
+            else
+            {
+                return hex;
+            }
         }
 
         /// <summary>
diff --git a/source/Cosmos.System2_Plugs/System/UInt64Impl.cs b/source/Cosmos.System2_Plugs/System/UInt64Impl.cs
index b764ebcd6..5bc7cacbe 100644
--- a/source/Cosmos.System2_Plugs/System/UInt64Impl.cs
+++ b/source/Cosmos.System2_Plugs/System/UInt64Impl.cs
@@ -1,5 +1,6 @@
 using System;
 using Cosmos.Common;
+using Cosmos.Common.Extensions;
 using IL2CPU.API;
 using IL2CPU.API.Attribs;
 
@@ -12,5 +13,21 @@ namespace Cosmos.System_Plugs.System
         {
             return StringHelper.GetNumberString(aThis);
         }
+        
+        public static string ToString(ref ulong aThis, string formating)
+        {
+            if(formating == "X")
+            {
+                return ToHexString.ToHex(aThis, false);
+            }
+            else if(formating == "G")
+            {
+                return ToString(ref aThis);
+            }
+            else
+            {
+                throw new NotImplementedException();
+            }
+        }
     }
 }