diff --git a/README b/README
index 4233db4..840a696 100644
--- a/README
+++ b/README
@@ -52,6 +52,12 @@ Windows builds can also be created using the autotools build system, using the
 MinGW-w64 toolchain from http://mingw-w64.sourceforge.net/ - either natively
 in Windows with the MSYS2 environment, or cross-compiling from another system.
 
+To build from MSYS2, the following packages must be installed: autoconf,
+automake-wrapper, libtool, make, and either mingw-w64-i686-gcc (for 32-bit)
+or mingw-w64-x86_64-gcc (for 64-bit). Open either the "MSYS2 MinGW 32-bit" or
+"MSYS2 MinGW 64-bit" command window from the Start menu and use this when
+configuring and building the package. The "MSYS2 MSYS" shell will not work.
+
 The "old" MinGW from http://mingw.org/ is not supported.
 
 API