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
@@ -2163,7 +2163,7 @@
 vm_object_coalesce(vm_object_t prev_object, vm_ooffset_t prev_offset,
     vm_size_t prev_size, vm_size_t next_size, boolean_t reserved)
 {
-	vm_pindex_t next_pindex;
+	vm_pindex_t next_end, next_pindex;
 
 	if (prev_object == NULL)
 		return (TRUE);
@@ -2197,10 +2197,12 @@
 		return (FALSE);
 	}
 
+	next_end = next_pindex + next_size;
+
 	/*
 	 * Account for the charge.
 	 */
-	if (prev_object->cred != NULL) {
+	if (prev_object->cred != NULL && next_end > prev_object->size) {
 		/*
 		 * If prev_object was charged, then this mapping,
 		 * although not charged now, may become writable
@@ -2211,38 +2213,27 @@
 		 * 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_end - 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;
 	}
 
 	/*
 	 * Remove any pages that may still be in the object from a previous
 	 * deallocation.
 	 */
-	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
-	}
+	if (next_pindex < prev_object->size)
+		vm_object_page_remove(prev_object, next_pindex, next_end, 0);
 
 	/*
 	 * Extend the object if necessary.
 	 */
-	if (next_pindex + next_size > prev_object->size)
-		prev_object->size = next_pindex + next_size;
+	if (next_end > prev_object->size)
+		prev_object->size = next_end;
 
 #ifdef INVARIANTS
 	/*
@@ -2254,7 +2245,7 @@
 		vm_pindex_t pidx;
 
 		pidx = swap_pager_seek_data(prev_object, next_pindex);
-		KASSERT(pidx >= next_pindex + next_size,
+		KASSERT(pidx >= next_end,
 		    ("found obj %p pindex %#jx e %#jx %#jx %#jx",
 		    prev_object, pidx, (uintmax_t)prev_offset,
 		    (uintmax_t)prev_size, (uintmax_t)next_size));