--- a/sys/vm/vm_mmap.c
+++ b/sys/vm/vm_mmap.c
@@ -788,7 +788,7 @@
 	vm_map_t map;
 	char *vec;
 	int error;
-	int vecindex, lastvecindex;
+	vm_pindex_t vecindex, lastvecindex;
 	vm_map_entry_t current;
 	vm_map_entry_t entry;
 	int mincoreinfo;
@@ -826,7 +826,7 @@
 	 * in the current processes address space, we can easily look
 	 * up the pages elsewhere.
 	 */
-	lastvecindex = -1;
+	lastvecindex = (vm_pindex_t)-1;
 	for (current = entry;
 	     current && current->ba.start < end;
 	     current = vm_map_rb_tree_RB_NEXT(current)) {
@@ -918,7 +918,7 @@
 			 * the byte vector is zeroed for those skipped entries.
 			 */
 			while((lastvecindex + 1) < vecindex) {
-				error = subyte( vec + lastvecindex, 0);
+				error = subyte(vec + lastvecindex + 1, 0);
 				if (error) {
 					error = EFAULT;
 					goto done;
@@ -959,7 +959,7 @@
 	 */
 	vecindex = OFF_TO_IDX(end - first_addr);
 	while((lastvecindex + 1) < vecindex) {
-		error = subyte( vec + lastvecindex, 0);
+		error = subyte(vec + lastvecindex + 1, 0);
 		if (error) {
 			error = EFAULT;
 			goto done;