diff --git a/sys/x86/include/xen/xen-os.h b/sys/x86/include/xen/xen-os.h
--- a/sys/x86/include/xen/xen-os.h
+++ b/sys/x86/include/xen/xen-os.h
@@ -30,6 +30,10 @@
 #ifndef _MACHINE_X86_XEN_XEN_OS_H_
 #define _MACHINE_X86_XEN_XEN_OS_H_
 
+#ifndef _XEN_XEN_OS_H_
+#error "do not #include machine/xen/xen-os.h, #include xen/xen-os.h instead"
+#endif
+
 /* Shared memory needs write-back as its cache attribute for coherency. */
 #define VM_MEMATTR_XEN VM_MEMATTR_WRITE_BACK
 
diff --git a/sys/x86/xen/xen_intr.c b/sys/x86/xen/xen_intr.c
--- a/sys/x86/xen/xen_intr.c
+++ b/sys/x86/xen/xen_intr.c
@@ -57,7 +57,6 @@
 #include <machine/stdarg.h>
 
 #include <machine/xen/synch_bitops.h>
-#include <machine/xen/xen-os.h>
 
 #include <xen/xen-os.h>
 #include <xen/hvm.h>
diff --git a/sys/xen/xen-os.h b/sys/xen/xen-os.h
--- a/sys/xen/xen-os.h
+++ b/sys/xen/xen-os.h
@@ -71,12 +71,6 @@
 
 	return (hvm_get_parameter(HVM_PARAM_CONSOLE_EVTCHN));
 }
-#endif
-
-#include <machine/xen/xen-os.h>
-
-/* Everything below this point is not included by assembler (.S) files. */
-#ifndef __ASSEMBLY__
 
 extern shared_info_t *HYPERVISOR_shared_info;
 
@@ -117,6 +111,12 @@
 
 	return (xen_domain() && (hvm_start_flags & SIF_INITDOMAIN) != 0);
 }
+#endif
+
+#include <machine/xen/xen-os.h>
+
+/* Everything below this point is not included by assembler (.S) files. */
+#ifndef __ASSEMBLY__
 
 /*
  * Based on ofed/include/linux/bitops.h