diff --git a/configure.ac b/configure.ac
index c5300beb2ba..95701b55704 100644
--- a/configure.ac
+++ b/configure.ac
@@ -5621,7 +5621,7 @@ case $opsys in
 esac
 
 case $opsys in
-  gnu-* | solaris )
+  gnu-* | solaris | cygwin )
     dnl FIXME Can't we test if this exists (eg /proc/$$)?
     AC_DEFINE([HAVE_PROCFS], [1], [Define if you have the /proc filesystem.])
   ;;