diff --git a/sys/amd64/include/xen/hypercall.h b/sys/amd64/include/xen/hypercall.h
--- a/sys/amd64/include/xen/hypercall.h
+++ b/sys/amd64/include/xen/hypercall.h
@@ -1,4 +1,6 @@
 /******************************************************************************
+ * SPDX-License-Identifier: MIT OR GPL-2.0-only
+ *
  * hypercall.h
  *
  * FreeBSD-specific hypervisor handling.
diff --git a/sys/i386/include/xen/hypercall.h b/sys/i386/include/xen/hypercall.h
--- a/sys/i386/include/xen/hypercall.h
+++ b/sys/i386/include/xen/hypercall.h
@@ -1,4 +1,6 @@
 /******************************************************************************
+ * SPDX-License-Identifier: MIT OR GPL-2.0-only
+ *
  * hypercall.h
  *
  * Linux-specific hypervisor handling.
diff --git a/sys/xen/gnttab.h b/sys/xen/gnttab.h
--- a/sys/xen/gnttab.h
+++ b/sys/xen/gnttab.h
@@ -1,4 +1,6 @@
 /******************************************************************************
+ * SPDX-License-Identifier: MIT OR GPL-2.0-only
+ *
  * gnttab.h
  * 
  * Two sets of functionality:
diff --git a/sys/xen/privcmd.h b/sys/xen/privcmd.h
--- a/sys/xen/privcmd.h
+++ b/sys/xen/privcmd.h
@@ -1,4 +1,6 @@
 /******************************************************************************
+ * SPDX-License-Identifier: MIT OR GPL-2.0-only
+ *
  * privcmd.h
  * 
  * Interface to /proc/xen/privcmd.