diff --git a/configure.ac b/configure.ac
index c708f70..db506ed 100644
--- a/configure.ac
+++ b/configure.ac
@@ -48,7 +48,8 @@ PKG_CHECK_MODULES(XORG, [xorg-server >= 1.19] xproto [inputproto >= 2.2])
 PKG_CHECK_MODULES(LIBINPUT, [libinput >= 1.11.0])
 
 PKG_CHECK_MODULES(INPUTPROTO24, [inputproto >= 2.3.99.1],
-		  [AC_DEFINE(HAVE_INPUTPROTO24, [1], [inputproto 2.4 is available])])
+		  [AC_DEFINE(HAVE_INPUTPROTO24, [1], [inputproto 2.4 is available])],
+		  [:])
 
 OLD_LIBS=$LIBS
 OLD_CFLAGS=$CFLAGS