diff --git a/configure b/configure
index aeb527e4b4..f6e5549a48 100755
--- a/configure
+++ b/configure
@@ -287,7 +287,7 @@ _confcygwin="TARGET_CYGWIN=no"
 _confwin32=
 if [ "$system_name" = "FreeBSD" ]; then
     _archlibs="-rdynamic -pthread"
-elif [ `echo $system_name | sed 's/CYGWIN.*/CYGWIN/i'` = "CYGWIN" ]; then
+elif [ `echo $system_name | sed 's/[cC][yY][gG][wW][iI][nN].*/CYGWIN/'` = "CYGWIN" ]; then
     _confcygwin="TARGET_CYGWIN=yes"
     _confwin32="#define WIN32"
     _archlibs="-lpthread"