diff --git a/sc2/INSTALL b/sc2/INSTALL
index 16341e030..9280791db 100644
--- a/sc2/INSTALL
+++ b/sc2/INSTALL
@@ -11,6 +11,7 @@ GNU Make 3.80
 
 For Windows:
 Microsoft Visual C++ 6 or 7 (or MinGW+MSYS, see INSTALL.mingw for that)
+Processor Pack 5 for VC6 (if using VC6, to build MMX-accelerated code)
 
 For Mac OS X:
 Apple Developer Tools (for Mac OS X 10.2 and older)