diff --git a/object-file.c b/object-file.c
index 6280e42f34..5615908967 100644
--- a/object-file.c
+++ b/object-file.c
@@ -509,7 +509,7 @@ cleanup:
 static void hash_object_body(const struct git_hash_algo *algo, struct git_hash_ctx *c,
 			     const void *buf, unsigned long len,
 			     struct object_id *oid,
-			     char *hdr, int *hdrlen)
+			     char *hdr, size_t *hdrlen)
 {
 	algo->init_fn(c);
 	git_hash_update(c, hdr, *hdrlen);
@@ -518,9 +518,9 @@ static void hash_object_body(const struct git_hash_algo *algo, struct git_hash_c
 }
 
 static void write_object_file_prepare(const struct git_hash_algo *algo,
-				      const void *buf, unsigned long len,
+				      const void *buf, size_t len,
 				      enum object_type type, struct object_id *oid,
-				      char *hdr, int *hdrlen)
+				      char *hdr, size_t *hdrlen)
 {
 	struct git_hash_ctx c;
 
@@ -663,11 +663,11 @@ out:
 }
 
 void hash_object_file(const struct git_hash_algo *algo, const void *buf,
-		      unsigned long len, enum object_type type,
+		      size_t len, enum object_type type,
 		      struct object_id *oid)
 {
 	char hdr[MAX_HEADER_LEN];
-	int hdrlen = sizeof(hdr);
+	size_t hdrlen = sizeof(hdr);
 
 	write_object_file_prepare(algo, buf, len, type, oid, hdr, &hdrlen);
 }
@@ -1108,7 +1108,7 @@ cleanup:
 }
 
 int odb_source_loose_write_object(struct odb_source *source,
-				  const void *buf, unsigned long len,
+				  const void *buf, size_t len,
 				  enum object_type type, struct object_id *oid,
 				  struct object_id *compat_oid_in, unsigned flags)
 {
@@ -1116,7 +1116,7 @@ int odb_source_loose_write_object(struct odb_source *source,
 	const struct git_hash_algo *compat = source->odb->repo->compat_hash_algo;
 	struct object_id compat_oid;
 	char hdr[MAX_HEADER_LEN];
-	int hdrlen = sizeof(hdr);
+	size_t hdrlen = sizeof(hdr);
 
 	/* Generate compat_oid */
 	if (compat) {
diff --git a/object-file.h b/object-file.h
index 1229d5f675..a5b7f9aa5b 100644
--- a/object-file.h
+++ b/object-file.h
@@ -65,7 +65,7 @@ int odb_source_loose_freshen_object(struct odb_source *source,
 				    const struct object_id *oid);
 
 int odb_source_loose_write_object(struct odb_source *source,
-				  const void *buf, unsigned long len,
+				  const void *buf, size_t len,
 				  enum object_type type, struct object_id *oid,
 				  struct object_id *compat_oid_in, unsigned flags);
 
@@ -177,7 +177,7 @@ int finalize_object_file_flags(struct repository *repo,
 			       enum finalize_object_file_flags flags);
 
 void hash_object_file(const struct git_hash_algo *algo, const void *buf,
-		      unsigned long len, enum object_type type,
+		      size_t len, enum object_type type,
 		      struct object_id *oid);
 
 /* Helper to check and "touch" a file */