diff --git a/sys/sys/refcount.h b/sys/sys/refcount.h
index 9788fdfeaa44..d15dbe08a7db 100644
--- a/sys/sys/refcount.h
+++ b/sys/sys/refcount.h
@@ -32,6 +32,15 @@
 #ifndef __SYS_REFCOUNT_H__
 #define __SYS_REFCOUNT_H__
 
+#include <machine/atomic.h>
+
+#ifdef _KERNEL
+#warning _KERNEL defined
+#include <sys/systm.h>
+#else
+#define	KASSERT(exp, msg)	/* */
+#endif
+
 static __inline void
 refcount_init(volatile u_int *count, u_int value)
 {
@@ -49,8 +58,12 @@ refcount_acquire(volatile u_int *count)
 static __inline int
 refcount_release(volatile u_int *count)
 {
+	u_int old;
 
-	return (atomic_fetchadd_int(count, -1) == 1);
+	/* XXX: Should this have a rel membar? */
+	old = atomic_fetchadd_int(count, -1);
+	KASSERT(old > 0, ("negative refcount %p", count));
+	return (old == 1);
 }
 
 #endif	/* ! __SYS_REFCOUNT_H__ */