diff --git a/sys/vm/vm_object.c b/sys/vm/vm_object.c
--- a/sys/vm/vm_object.c
+++ b/sys/vm/vm_object.c
@@ -2200,7 +2200,8 @@
 	/*
 	 * Account for the charge.
 	 */
-	if (prev_object->cred != NULL) {
+	if (prev_object->cred != NULL &&
+	    next_pindex + next_size > prev_object->size) {
 		/*
 		 * If prev_object was charged, then this mapping,
 		 * although not charged now, may become writable
@@ -2211,12 +2212,14 @@
 		 * entry, and swap reservation for this entry is
 		 * managed in appropriate time.
 		 */
-		if (!reserved && !swap_reserve_by_cred(ptoa(next_size),
-		    prev_object->cred)) {
+		vm_size_t charge = ptoa(next_pindex + next_size -
+		    prev_object->size);
+		if (!reserved &&
+		    !swap_reserve_by_cred(charge, prev_object->cred)) {
 			VM_OBJECT_WUNLOCK(prev_object);
 			return (FALSE);
 		}
-		prev_object->charge += ptoa(next_size);
+		prev_object->charge += charge;
 	}
 
 	/*
@@ -2226,16 +2229,6 @@
 	if (next_pindex < prev_object->size) {
 		vm_object_page_remove(prev_object, next_pindex, next_pindex +
 		    next_size, 0);
-#if 0
-		if (prev_object->cred != NULL) {
-			KASSERT(prev_object->charge >=
-			    ptoa(prev_object->size - next_pindex),
-			    ("object %p overcharged 1 %jx %jx", prev_object,
-				(uintmax_t)next_pindex, (uintmax_t)next_size));
-			prev_object->charge -= ptoa(prev_object->size -
-			    next_pindex);
-		}
-#endif
 	}
 
 	/*