diff --git a/llvm/autoconf/configure.ac b/llvm/autoconf/configure.ac
index 4ca4296cc6e2ed53fd9c1c3c2a21961ce0309d97..1335306b70a6337e13f7ff311dc2883b022b206d 100644
--- a/llvm/autoconf/configure.ac
+++ b/llvm/autoconf/configure.ac
@@ -110,6 +110,10 @@ case $build in
              AC_SUBST(OS,[Win32])
              platform_type="Win32"
 	     ;;
+        *-*-mingw*)
+             AC_SUBST(OS,[Win32])
+             platform_type="Win32"
+	     ;;
 	*)   
              AC_SUBST(OS,[Unknown])
              platform_type="Unknown"