diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index bef1305ce4..83b0431c21 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -1917,7 +1917,7 @@ struct pbase_tree_cache {
 	int ref;
 	int temporary;
 	void *tree_data;
-	unsigned long tree_size;
+	size_t tree_size;
 };
 
 static struct pbase_tree_cache *(pbase_tree_cache[256]);
@@ -1944,8 +1944,7 @@ static struct pbase_tree_cache *pbase_tree_get(const struct object_id *oid)
 {
 	struct pbase_tree_cache *ent, *nent;
 	void *data;
-	unsigned long size;
-	size_t size_st = 0;
+	size_t size;
 	enum object_type type;
 	int neigh;
 	int my_ix = pbase_tree_cache_ix(oid);
@@ -1973,8 +1972,7 @@ static struct pbase_tree_cache *pbase_tree_get(const struct object_id *oid)
 	/* Did not find one.  Either we got a bogus request or
 	 * we need to read and perhaps cache.
 	 */
-	data = odb_read_object(the_repository->objects, oid, &type, &size_st);
-	size = cast_size_t_to_ulong(size_st);
+	data = odb_read_object(the_repository->objects, oid, &type, &size);
 	if (!data)
 		return NULL;
 	if (type != OBJ_TREE) {
@@ -2128,16 +2126,14 @@ static void add_preferred_base(struct object_id *oid)
 {
 	struct pbase_tree *it;
 	void *data;
-	unsigned long size;
-	size_t size_st = 0;
+	size_t size;
 	struct object_id tree_oid;
 
 	if (window <= num_preferred_base++)
 		return;
 
 	data = odb_read_object_peeled(the_repository->objects, oid,
-				      OBJ_TREE, &size_st, &tree_oid);
-	size = cast_size_t_to_ulong(size_st);
+				      OBJ_TREE, &size, &tree_oid);
 	if (!data)
 		return;
 
diff --git a/tree-walk.c b/tree-walk.c
index a67f06b9eb..e2cea5d883 100644
--- a/tree-walk.c
+++ b/tree-walk.c
@@ -49,7 +49,7 @@ static int decode_tree_entry(struct tree_desc *desc, const char *buf, unsigned l
 
 static int init_tree_desc_internal(struct tree_desc *desc,
 				   const struct object_id *oid,
-				   const void *buffer, unsigned long size,
+				   const void *buffer, size_t size,
 				   struct strbuf *err,
 				   enum tree_desc_flags flags)
 {
@@ -63,7 +63,7 @@ static int init_tree_desc_internal(struct tree_desc *desc,
 }
 
 void init_tree_desc(struct tree_desc *desc, const struct object_id *tree_oid,
-		    const void *buffer, unsigned long size)
+		    const void *buffer, size_t size)
 {
 	struct strbuf err = STRBUF_INIT;
 	if (init_tree_desc_internal(desc, tree_oid, buffer, size, &err, 0))
@@ -72,7 +72,7 @@ void init_tree_desc(struct tree_desc *desc, const struct object_id *tree_oid,
 }
 
 int init_tree_desc_gently(struct tree_desc *desc, const struct object_id *oid,
-			  const void *buffer, unsigned long size,
+			  const void *buffer, size_t size,
 			  enum tree_desc_flags flags)
 {
 	struct strbuf err = STRBUF_INIT;
@@ -777,8 +777,7 @@ enum get_oid_result get_tree_entry_follow_symlinks(struct repository *r,
 			goto done;
 		} else if (S_ISLNK(*mode)) {
 			/* Follow a symlink */
-			unsigned long link_len;
-			size_t link_len_st = 0;
+			size_t link_len;
 			size_t len;
 			char *contents, *contents_start;
 			struct dir_state *parent;
@@ -798,8 +797,7 @@ enum get_oid_result get_tree_entry_follow_symlinks(struct repository *r,
 
 			contents = odb_read_object(r->objects,
 						   &current_tree_oid, &type,
-						   &link_len_st);
-			link_len = cast_size_t_to_ulong(link_len_st);
+						   &link_len);
 
 			if (!contents)
 				goto done;
diff --git a/tree-walk.h b/tree-walk.h
index 9646c47ac5..af6e82fd3f 100644
--- a/tree-walk.h
+++ b/tree-walk.h
@@ -85,10 +85,10 @@ int update_tree_entry_gently(struct tree_desc *);
  * members of `struct tree`.
  */
 void init_tree_desc(struct tree_desc *desc, const struct object_id *tree_oid,
-		    const void *buf, unsigned long size);
+		    const void *buf, size_t size);
 
 int init_tree_desc_gently(struct tree_desc *desc, const struct object_id *oid,
-			  const void *buf, unsigned long size,
+			  const void *buf, size_t size,
 			  enum tree_desc_flags flags);
 
 /*
diff --git a/tree.c b/tree.c
index 53f7395e9f..d37b9bc7b1 100644
--- a/tree.c
+++ b/tree.c
@@ -172,7 +172,7 @@ struct tree *lookup_tree(struct repository *r, const struct object_id *oid)
 	return object_as_type(obj, OBJ_TREE, 0);
 }
 
-int parse_tree_buffer(struct tree *item, void *buffer, unsigned long size)
+int parse_tree_buffer(struct tree *item, void *buffer, size_t size)
 {
 	if (item->object.parsed)
 		return 0;
diff --git a/tree.h b/tree.h
index 677382eed8..50f0b15af4 100644
--- a/tree.h
+++ b/tree.h
@@ -10,14 +10,14 @@ struct strbuf;
 struct tree {
 	struct object object;
 	void *buffer;
-	unsigned long size;
+	size_t size;
 };
 
 extern const char *tree_type;
 
 struct tree *lookup_tree(struct repository *r, const struct object_id *oid);
 
-int parse_tree_buffer(struct tree *item, void *buffer, unsigned long size);
+int parse_tree_buffer(struct tree *item, void *buffer, size_t size);
 
 #define parse_tree_gently(t, q) repo_parse_tree_gently(the_repository, t, q)
 int repo_parse_tree_gently(struct repository *r, struct tree *item,