diff --git a/Map-Compilers.md b/Map-Compilers.md
index becda5a..ec22b24 100644
--- a/Map-Compilers.md
+++ b/Map-Compilers.md
@@ -37,4 +37,10 @@ Here's an actual list of changes Mapbase makes to the compile tools:
 
 ### VRAD
 
-* Fixed useless debug counter (from [the famous debug counter fix](https://github.com/ValveSoftware/source-sdk-2013/pull/436))
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+* Fixed useless debug counter (from [the famous debug counter fix](https://github.com/ValveSoftware/source-sdk-2013/pull/436))
+
+## Using other compilers
+
+The main reason Mapbase maps cannot be compiled using the original compile tools is because the original VBSP does not recognize custom shaders and therefore cannot mark faces with them for lightmap compilation. This is fixed by changing the way the material system is initialized in VBSP so it loads mod shaders. Mapbase and Slammin' Source compilers already use this fix, so they're usually said to be the required tools, but technically all you need is a version of VBSP which uses this patch.
+
+For more information, please see [this issue reply on the original Source 2013 repository](https://github.com/ValveSoftware/source-sdk-2013/issues/154#issuecomment-22601176).
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