diff --git a/configure.ac b/configure.ac
index 1253c26f..dc684fb1 100644
--- a/configure.ac
+++ b/configure.ac
@@ -339,8 +339,13 @@ case $host in
     #AC_SUBST(OS_MACOS)
     ;;
 
+    *-freebsd1*)
+    AC_MSG_RESULT([FreeBSD-1x])
+    ADDITIONAL_CFLAGS="-D_GNU_SOURCE -DWITH_POSIX"
+    ;;
+
     *)
-    AC_MSG_WARN([==> Currently unsupported operating system ${host}!])
+    AC_MSG_WARN([==> Currently unsupported operating system '${host}' !])
     AC_MSG_ERROR([==> If you can provide patches to support your operating system please write to 'libcoap-developers@lists.sourceforge.net'.])
 esac