diff --git a/sys/vm/vm_page.c b/sys/vm/vm_page.c
--- a/sys/vm/vm_page.c
+++ b/sys/vm/vm_page.c
@@ -750,8 +750,7 @@
 	 * physical pages.
 	 */
 	for (i = 0; phys_avail[i + 1] != 0; i += 2)
-		if (vm_phys_avail_size(i) != 0)
-			vm_phys_add_seg(phys_avail[i], phys_avail[i + 1]);
+		vm_phys_add_seg(phys_avail[i], phys_avail[i + 1]);
 
 	/*
 	 * Initialize the physical memory allocator.
diff --git a/sys/vm/vm_phys.c b/sys/vm/vm_phys.c
--- a/sys/vm/vm_phys.c
+++ b/sys/vm/vm_phys.c
@@ -476,10 +476,18 @@
 {
 	vm_paddr_t paddr;
 
-	KASSERT((start & PAGE_MASK) == 0,
-	    ("vm_phys_define_seg: start is not page aligned"));
-	KASSERT((end & PAGE_MASK) == 0,
-	    ("vm_phys_define_seg: end is not page aligned"));
+	if ((start & PAGE_MASK) != 0)
+		panic("%s: start (%jx) is not page aligned", __func__,
+		    (uintmax_t)start);
+	if ((end & PAGE_MASK) != 0)
+		panic("%s: end (%jx) is not page aligned", __func__,
+		    (uintmax_t)end);
+	if (start > end)
+		panic("%s: start (%jx) > end (%jx)!", __func__,
+		    (uintmax_t)start, (uintmax_t)end);
+
+	if (start == end)
+		return;
 
 	/*
 	 * Split the physical memory segment if it spans two or more free