Index: sys/kern/subr_rman.c
===================================================================
--- sys/kern/subr_rman.c
+++ sys/kern/subr_rman.c
@@ -160,6 +160,11 @@
 	    rm->rm_descr, start, end));
 	if (start < rm->rm_start || end > rm->rm_end)
 		return EINVAL;
+#if defined(INVARIANTS) || defined(_STANDALONE)
+	if (RMAN_IS_DEFAULT_RANGE(start, end))
+		printf("ERROR: %s: <%s> attempting to manage default range\n",
+		    __func__, rm->rm_descr);
+#endif
 	r = int_alloc_resource(M_NOWAIT);
 	if (r == NULL)
 		return ENOMEM;
@@ -447,6 +452,8 @@
 	       dev == NULL ? "<null>" : device_get_nameunit(dev)));
 	KASSERT((flags & RF_FIRSTSHARE) == 0,
 	    ("invalid flags %#x", flags));
+	KASSERT(count != 0, ("%s(): attempting to allocate empty range",
+	    __func__));
 	new_rflags = (flags & ~RF_FIRSTSHARE) | RF_ALLOCATED;
 
 	mtx_lock(rm->rm_mtx);