diff --git a/wmlongrun/configure.ac b/wmlongrun/configure.ac
index 3b48676..ce483a8 100644
--- a/wmlongrun/configure.ac
+++ b/wmlongrun/configure.ac
@@ -86,7 +86,7 @@ case ${host_os} in
 linux*)
   SETUID_FLAGS="-m 4755 -o root -g root"
   OS=linux
-  AC_DEFINE(LINUX)
+  AC_DEFINE([LINUX], [1], [use Linux specific code])
   ;;
 freebsd*)
   OS=freebsd