diff --git a/combine-diff.c b/combine-diff.c
index fb72174918..4915bf335d 100644
--- a/combine-diff.c
+++ b/combine-diff.c
@@ -304,7 +304,7 @@ static struct lline *coalesce_lines(struct lline *base, int *lenbase,
 
 static char *grab_blob(struct repository *r,
 		       const struct object_id *oid, unsigned int mode,
-		       unsigned long *size, struct userdiff_driver *textconv,
+		       size_t *size, struct userdiff_driver *textconv,
 		       const char *path)
 {
 	char *blob;
@@ -325,9 +325,7 @@ static char *grab_blob(struct repository *r,
 		*size = fill_textconv(r, textconv, df, &blob);
 		free_filespec(df);
 	} else {
-		size_t size_st = 0;
-		blob = odb_read_object(r->objects, oid, &type, &size_st);
-		*size = cast_size_t_to_ulong(size_st);
+		blob = odb_read_object(r->objects, oid, &type, size);
 		if (!blob)
 			die(_("unable to read %s"), oid_to_hex(oid));
 		if (type != OBJ_BLOB)
@@ -431,7 +429,7 @@ static void combine_diff(struct repository *r,
 	xdemitconf_t xecfg;
 	mmfile_t parent_file;
 	struct combine_diff_state state;
-	unsigned long sz;
+	size_t sz;
 
 	if (result_deleted)
 		return; /* result deleted */
@@ -1015,7 +1013,7 @@ static void show_patch_diff(struct combine_diff_path *elem, int num_parent,
 			    struct rev_info *rev)
 {
 	struct diff_options *opt = &rev->diffopt;
-	unsigned long result_size, cnt, lno;
+	size_t result_size, cnt, lno;
 	int result_deleted = 0;
 	char *result, *cp;
 	struct sline *sline; /* survived lines */
@@ -1134,7 +1132,7 @@ static void show_patch_diff(struct combine_diff_path *elem, int num_parent,
 		is_binary = buffer_is_binary(result, result_size);
 		for (i = 0; !is_binary && i < num_parent; i++) {
 			char *buf;
-			unsigned long size;
+			size_t size;
 			buf = grab_blob(opt->repo,
 					&elem->parent[i].oid,
 					elem->parent[i].mode,