diff --git a/sys/amd64/conf/GENERIC b/sys/amd64/conf/GENERIC
--- a/sys/amd64/conf/GENERIC
+++ b/sys/amd64/conf/GENERIC
@@ -380,9 +380,11 @@
 device		hyperv			# HyperV drivers 
 
 # Xen HVM Guest Optimizations
-# NOTE: XENHVM depends on xenpci.  They must be added or removed together.
+# NOTE: XENHVM and xenpci interdepend.  They must be added or removed
+# together.  xentimer depends on XENHVM and isn't required.
 options 	XENHVM			# Xen HVM kernel infrastructure
 device		xenpci			# Xen HVM Hypervisor services driver
+device		xentimer		# Xen x86 PV timer device
 
 # Netmap provides direct access to TX/RX rings on supported NICs
 device		netmap			# netmap(4) support
diff --git a/sys/conf/files b/sys/conf/files
--- a/sys/conf/files
+++ b/sys/conf/files
@@ -3548,8 +3548,8 @@
 dev/xen/grant_table/grant_table.c	optional xenhvm
 dev/xen/netback/netback.c	optional xenhvm
 dev/xen/netfront/netfront.c	optional xenhvm
+dev/xen/timer/timer.c		optional xenhvm xentimer
 dev/xen/xenpci/xenpci.c		optional xenpci
-dev/xen/timer/timer.c		optional xenhvm
 dev/xen/xenstore/xenstore.c	optional xenhvm
 dev/xen/xenstore/xenstore_dev.c	optional xenhvm
 dev/xen/xenstore/xenstored_dev.c	optional xenhvm
diff --git a/sys/i386/conf/GENERIC b/sys/i386/conf/GENERIC
--- a/sys/i386/conf/GENERIC
+++ b/sys/i386/conf/GENERIC
@@ -343,9 +343,11 @@
 device		hyperv			# HyperV drivers
 
 # Xen HVM Guest Optimizations
-# NOTE: XENHVM depends on xenpci.  They must be added or removed together.
+# NOTE: XENHVM and xenpci interdepend.  They must be added or removed
+# together.  xentimer depends on XENHVM and isn't required.
 options 	XENHVM			# Xen HVM kernel infrastructure
 device		xenpci			# Xen HVM Hypervisor services driver
+device		xentimer		# Xen x86 PV timer device
 
 # evdev interface
 options 	EVDEV_SUPPORT		# evdev support in legacy drivers