diff --git a/autoconf/configure.ac b/autoconf/configure.ac
index 0e9e31810e7..64c5b627c72 100644
--- a/autoconf/configure.ac
+++ b/autoconf/configure.ac
@@ -103,6 +103,9 @@ case $build in
 	           AC_SUBST(LLVMGCCDIR,[/home/vadve/lattner/local/sparc/llvm-gcc/])
 			 fi
 	         ;;
+	*-*-cygwin*)
+             AC_SUBST(OS,[Cygwin])
+	         ;;
 
 	*-*-darwin*)
              AC_SUBST(OS,[Darwin])
diff --git a/configure b/configure
index bc51db02306..139648d530d 100755
--- a/configure
+++ b/configure
@@ -1869,6 +1869,10 @@ case $build in
              OS=Darwin
 
 	         ;;
+	*-*-cygwin*)
+             OS=Cygwin
+
+	         ;;
 
 	*)       OS=Unknown