Update README.md

Author: GrahamTheCoder

README.md

@@ -5,7 +5,7 @@ Convert code from VB.NET to C# and vice versa via Roslyn using a [Visual Studio
 ## Visual Studio Extension
 Adds context menu items to convert projects/files between VB.NET and C#. See the [wiki documentation](https://github.com/icsharpcode/CodeConverter/wiki) for help using it.
 
-[Download from Visual Studio Marketplace](https://marketplace.visualstudio.com/items?itemName=SharpDevelopTeam.CodeConverter)
+[Download from Visual Studio Marketplace](https://marketplace.visualstudio.com/items?itemName=SharpDevelopTeam.CodeConverter) (Requires VS 2017 15.9.3+)
 
 * Flexible: Convert a small selection, or a whole solution in one go, in either direction.
 * Accurate: Full project context (through Roslyn) is used to get the most accurate conversion.