diff --git a/master/Kbuild.in b/master/Kbuild.in
index 8ec1c573..f03519e3 100644
--- a/master/Kbuild.in
+++ b/master/Kbuild.in
@@ -85,7 +85,7 @@ ec_master-objs += rtdm.o
 endif
 
 ifeq (@ENABLE_XENOMAI@, 1)
-CFLAGS_rtdm.o := -I@XENOMAI_DIR@/include
+CFLAGS_rtdm.o := @XENOMAI_RTDM_CFLAGS@
 endif
 
 ifeq (@ENABLE_RTAI@, 1)