diff --git a/Makefile.in b/Makefile.in
index d201fbf59a..a68b3b2c49 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -12,7 +12,7 @@ NULL = /dev/null
 srcdir = @srcdir@
 top_srcdir = $(srcdir)
 hdrdir = $(srcdir)/include
-PLATFORM_DIR = win32
+PLATFORM_DIR = @PLATFORM_DIR@
 
 CC = @CC@
 CPP = @CPP@
diff --git a/configure.in b/configure.in
index 8555395f74..bfd9f49fac 100644
--- a/configure.in
+++ b/configure.in
@@ -2626,6 +2626,7 @@ AS_CASE(["$target_os"],
 #	    COMMON_MACROS="WIN32_LEAN_AND_MEAN="
 	    COMMON_HEADERS="winsock2.h windows.h"
 	    THREAD_MODEL=win32
+	    PLATFORM_DIR=win32
 	    ])
 	LIBRUBY_ALIASES=''
 	FIRSTMAKEFILE=GNUmakefile:cygwin/GNUmakefile.in
@@ -2776,6 +2777,7 @@ AC_SUBST(EXPORT_PREFIX)
 AC_SUBST(SYMBOL_PREFIX)
 AC_SUBST(MINIOBJS)
 AC_SUBST(THREAD_MODEL)
+AC_SUBST(PLATFORM_DIR)
 
 MAKEFILES="Makefile `echo $FIRSTMAKEFILE | sed 's/:.*//'`"
 MAKEFILES="`echo $MAKEFILES`"