diff --git a/README.win32.md b/README.win32.md
index 65f9e78e7..7f11e571e 100644
--- a/README.win32.md
+++ b/README.win32.md
@@ -30,17 +30,16 @@ On Windows setting up a correct build environment is very similar to typing
 The following preprocessor macros are to be used for conditional
 compilation related to Win32 in GLib-using code:
 
-- `G_OS_WIN32` is defined when compiling for native Win32, without
-  any POSIX emulation, other than to the extent provided by the
-  bundled Microsoft C library.
+- `G_OS_WIN32` and `G_PLATFORM_WIN32` are defined when compiling for native
+  Win32, without any POSIX emulation, other than to the extent provided by
+  the bundled Microsoft C library.  Either can be used to check when
+  conditionally compiling GLib-using code for Win32.
 
 - `G_WITH_CYGWIN` is defined if compiling for the Cygwin
   environment. Note that `G_OS_WIN32` is *not* defined in that case, as
   Cygwin is supposed to behave like Unix. `G_OS_UNIX` *is* defined by a GLib
-  for Cygwin.
-
-- `G_PLATFORM_WIN32` is defined when either `G_OS_WIN32` or `G_WITH_CYGWIN`
-  is defined.
+  for Cygwin, but `G_PLATFORM_WIN32` is *no longer* defined by GLib for
+  Cygwin.
 
 These macros are defined in `glibconfig.h`, and are thus available in
 all source files that include `<glib.h>`.