diff --git a/diff.h b/diff.h
index 9443dc1b00..e0c0af6286 100644
--- a/diff.h
+++ b/diff.h
@@ -431,11 +431,11 @@ struct combine_diff_path *diff_tree_paths(
 	struct combine_diff_path *p, const struct object_id *oid,
 	const struct object_id **parents_oid, int nparent,
 	struct strbuf *base, struct diff_options *opt);
-int diff_tree_oid(const struct object_id *old_oid,
-		  const struct object_id *new_oid,
-		  const char *base, struct diff_options *opt);
-int diff_root_tree_oid(const struct object_id *new_oid, const char *base,
-		       struct diff_options *opt);
+void diff_tree_oid(const struct object_id *old_oid,
+		   const struct object_id *new_oid,
+		   const char *base, struct diff_options *opt);
+void diff_root_tree_oid(const struct object_id *new_oid, const char *base,
+			struct diff_options *opt);
 
 struct combine_diff_path {
 	struct combine_diff_path *next;
diff --git a/revision.c b/revision.c
index cbf4b61aa6..c644c66091 100644
--- a/revision.c
+++ b/revision.c
@@ -791,9 +791,7 @@ static int rev_compare_tree(struct rev_info *revs,
 
 	tree_difference = REV_TREE_SAME;
 	revs->pruning.flags.has_changes = 0;
-	if (diff_tree_oid(&t1->object.oid, &t2->object.oid, "",
-			   &revs->pruning) < 0)
-		return REV_TREE_DIFFERENT;
+	diff_tree_oid(&t1->object.oid, &t2->object.oid, "", &revs->pruning);
 
 	if (!nth_parent)
 		if (bloom_ret == 1 && tree_difference == REV_TREE_SAME)
@@ -804,7 +802,6 @@ static int rev_compare_tree(struct rev_info *revs,
 
 static int rev_same_tree_as_empty(struct rev_info *revs, struct commit *commit)
 {
-	int retval;
 	struct tree *t1 = get_commit_tree(commit);
 
 	if (!t1)
@@ -812,9 +809,9 @@ static int rev_same_tree_as_empty(struct rev_info *revs, struct commit *commit)
 
 	tree_difference = REV_TREE_SAME;
 	revs->pruning.flags.has_changes = 0;
-	retval = diff_tree_oid(NULL, &t1->object.oid, "", &revs->pruning);
+	diff_tree_oid(NULL, &t1->object.oid, "", &revs->pruning);
 
-	return retval >= 0 && (tree_difference == REV_TREE_SAME);
+	return tree_difference == REV_TREE_SAME;
 }
 
 struct treesame_state {
diff --git a/tree-diff.c b/tree-diff.c
index f3d303c6e5..6ebad1a46f 100644
--- a/tree-diff.c
+++ b/tree-diff.c
@@ -29,9 +29,9 @@ static struct combine_diff_path *ll_diff_tree_paths(
 	struct combine_diff_path *p, const struct object_id *oid,
 	const struct object_id **parents_oid, int nparent,
 	struct strbuf *base, struct diff_options *opt);
-static int ll_diff_tree_oid(const struct object_id *old_oid,
-			    const struct object_id *new_oid,
-			    struct strbuf *base, struct diff_options *opt);
+static void ll_diff_tree_oid(const struct object_id *old_oid,
+			     const struct object_id *new_oid,
+			     struct strbuf *base, struct diff_options *opt);
 
 /*
  * Compare two tree entries, taking into account only path/S_ISDIR(mode),
@@ -679,9 +679,9 @@ static void try_to_follow_renames(const struct object_id *old_oid,
 	q->nr = 1;
 }
 
-static int ll_diff_tree_oid(const struct object_id *old_oid,
-			    const struct object_id *new_oid,
-			    struct strbuf *base, struct diff_options *opt)
+static void ll_diff_tree_oid(const struct object_id *old_oid,
+			     const struct object_id *new_oid,
+			     struct strbuf *base, struct diff_options *opt)
 {
 	struct combine_diff_path phead, *p;
 	pathchange_fn_t pathchange_old = opt->pathchange;
@@ -697,29 +697,27 @@ static int ll_diff_tree_oid(const struct object_id *old_oid,
 	}
 
 	opt->pathchange = pathchange_old;
-	return 0;
 }
 
-int diff_tree_oid(const struct object_id *old_oid,
-		  const struct object_id *new_oid,
-		  const char *base_str, struct diff_options *opt)
+void diff_tree_oid(const struct object_id *old_oid,
+		   const struct object_id *new_oid,
+		   const char *base_str, struct diff_options *opt)
 {
 	struct strbuf base;
-	int retval;
 
 	strbuf_init(&base, PATH_MAX);
 	strbuf_addstr(&base, base_str);
 
-	retval = ll_diff_tree_oid(old_oid, new_oid, &base, opt);
+	ll_diff_tree_oid(old_oid, new_oid, &base, opt);
 	if (!*base_str && opt->flags.follow_renames && diff_might_be_rename())
 		try_to_follow_renames(old_oid, new_oid, &base, opt);
 
 	strbuf_release(&base);
-
-	return retval;
 }
 
-int diff_root_tree_oid(const struct object_id *new_oid, const char *base, struct diff_options *opt)
+void diff_root_tree_oid(const struct object_id *new_oid,
+			const char *base,
+			struct diff_options *opt)
 {
-	return diff_tree_oid(NULL, new_oid, base, opt);
+	diff_tree_oid(NULL, new_oid, base, opt);
 }