diff --git a/sys/dev/extres/phy/phy_usb.c b/sys/dev/extres/phy/phy_usb.c
index 891db493634..ce25993482a 100644
--- a/sys/dev/extres/phy/phy_usb.c
+++ b/sys/dev/extres/phy/phy_usb.c
@@ -28,6 +28,7 @@
 __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
+#include <sys/systm.h>
 #include <sys/kernel.h>
 #include <sys/lock.h>
 #include <sys/queue.h>