diff --git a/lib/diff.c b/lib/diff.c
index 1a28335faf..6f50c0822c 100644
--- a/lib/diff.c
+++ b/lib/diff.c
@@ -4734,9 +4734,8 @@ int diff_populate_filespec(struct repository *r,
 		}
 	}
 	else {
-		size_t size_st = 0;
 		struct object_info info = {
-			.sizep = &size_st
+			.sizep = &s->size
 		};
 
 		if (!(size_only || check_binary))
@@ -4758,7 +4757,6 @@ int diff_populate_filespec(struct repository *r,
 			die("unable to read %s", oid_to_hex(&s->oid));
 
 object_read:
-		s->size = cast_size_t_to_ulong(size_st);
 		if (size_only || check_binary) {
 			if (size_only)
 				return 0;
@@ -4773,7 +4771,6 @@ object_read:
 			if (odb_read_object_info_extended(r->objects, &s->oid, &info,
 							  OBJECT_INFO_LOOKUP_REPLACE))
 				die("unable to read %s", oid_to_hex(&s->oid));
-			s->size = cast_size_t_to_ulong(size_st);
 		}
 		s->should_free = 1;
 	}
diff --git a/lib/diffcore.h b/lib/diffcore.h
index d75038d1b3..85fc94e2a5 100644
--- a/lib/diffcore.h
+++ b/lib/diffcore.h
@@ -54,7 +54,7 @@ struct diff_filespec {
 	char *path;
 	void *data;
 	void *cnt_data;
-	unsigned long size;
+	size_t size;
 	int count;               /* Reference count */
 	int rename_used;         /* Count of rename users */
 	unsigned short mode;	 /* file mode */