diff --git a/revision.c b/revision.c
index 60421f3a10..5de739384a 100644
--- a/revision.c
+++ b/revision.c
@@ -27,6 +27,7 @@
 #include "commit-reach.h"
 #include "commit-graph.h"
 #include "prio-queue.h"
+#include "hashmap.h"
 
 volatile show_early_output_fn_t show_early_output;
 
@@ -99,29 +100,146 @@ void mark_tree_uninteresting(struct repository *r, struct tree *tree)
 	mark_tree_contents_uninteresting(r, tree);
 }
 
+struct path_and_oids_entry {
+	struct hashmap_entry ent;
+	char *path;
+	struct oidset trees;
+};
+
+static int path_and_oids_cmp(const void *hashmap_cmp_fn_data,
+			     const struct path_and_oids_entry *e1,
+			     const struct path_and_oids_entry *e2,
+			     const void *keydata)
+{
+	return strcmp(e1->path, e2->path);
+}
+
+static void paths_and_oids_init(struct hashmap *map)
+{
+	hashmap_init(map, (hashmap_cmp_fn) path_and_oids_cmp, NULL, 0);
+}
+
+static void paths_and_oids_clear(struct hashmap *map)
+{
+	struct hashmap_iter iter;
+	struct path_and_oids_entry *entry;
+	hashmap_iter_init(map, &iter);
+
+	while ((entry = (struct path_and_oids_entry *)hashmap_iter_next(&iter))) {
+		oidset_clear(&entry->trees);
+		free(entry->path);
+	}
+
+	hashmap_free(map, 1);
+}
+
+static void paths_and_oids_insert(struct hashmap *map,
+				  const char *path,
+				  const struct object_id *oid)
+{
+	int hash = strhash(path);
+	struct path_and_oids_entry key;
+	struct path_and_oids_entry *entry;
+
+	hashmap_entry_init(&key, hash);
+
+	/* use a shallow copy for the lookup */
+	key.path = (char *)path;
+	oidset_init(&key.trees, 0);
+
+	if (!(entry = (struct path_and_oids_entry *)hashmap_get(map, &key, NULL))) {
+		entry = xcalloc(1, sizeof(struct path_and_oids_entry));
+		hashmap_entry_init(entry, hash);
+		entry->path = xstrdup(key.path);
+		oidset_init(&entry->trees, 16);
+		hashmap_put(map, entry);
+	}
+
+	oidset_insert(&entry->trees, oid);
+}
+
+static void add_children_by_path(struct repository *r,
+				 struct tree *tree,
+				 struct hashmap *map)
+{
+	struct tree_desc desc;
+	struct name_entry entry;
+
+	if (!tree)
+		return;
+
+	if (parse_tree_gently(tree, 1) < 0)
+		return;
+
+	init_tree_desc(&desc, tree->buffer, tree->size);
+	while (tree_entry(&desc, &entry)) {
+		switch (object_type(entry.mode)) {
+		case OBJ_TREE:
+			paths_and_oids_insert(map, entry.path, entry.oid);
+
+			if (tree->object.flags & UNINTERESTING) {
+				struct tree *child = lookup_tree(r, entry.oid);
+				if (child)
+					child->object.flags |= UNINTERESTING;
+			}
+			break;
+		case OBJ_BLOB:
+			if (tree->object.flags & UNINTERESTING) {
+				struct blob *child = lookup_blob(r, entry.oid);
+				if (child)
+					child->object.flags |= UNINTERESTING;
+			}
+			break;
+		default:
+			/* Subproject commit - not in this repository */
+			break;
+		}
+	}
+
+	free_tree_buffer(tree);
+}
+
 void mark_trees_uninteresting_sparse(struct repository *r,
 				     struct oidset *trees)
 {
+	unsigned has_interesting = 0, has_uninteresting = 0;
+	struct hashmap map;
+	struct hashmap_iter map_iter;
+	struct path_and_oids_entry *entry;
 	struct object_id *oid;
 	struct oidset_iter iter;
 
 	oidset_iter_init(trees, &iter);
-	while ((oid = oidset_iter_next(&iter))) {
+	while ((!has_interesting || !has_uninteresting) &&
+	       (oid = oidset_iter_next(&iter))) {
 		struct tree *tree = lookup_tree(r, oid);
 
 		if (!tree)
 			continue;
 
-		if (tree->object.flags & UNINTERESTING) {
-			/*
-			 * Remove the flag so the next call
-			 * is not a no-op. The flag is added
-			 * in mark_tree_unintersting().
-			 */
-			tree->object.flags ^= UNINTERESTING;
-			mark_tree_uninteresting(r, tree);
-		}
+		if (tree->object.flags & UNINTERESTING)
+			has_uninteresting = 1;
+		else
+			has_interesting = 1;
 	}
+
+	/* Do not walk unless we have both types of trees. */
+	if (!has_uninteresting || !has_interesting)
+		return;
+
+	paths_and_oids_init(&map);
+
+	oidset_iter_init(trees, &iter);
+	while ((oid = oidset_iter_next(&iter))) {
+		struct tree *tree = lookup_tree(r, oid);
+		add_children_by_path(r, tree, &map);
+	}
+
+	hashmap_iter_init(&map, &map_iter);
+	while ((entry = hashmap_iter_next(&map_iter)))
+		mark_trees_uninteresting_sparse(r, &entry->trees);
+
+	paths_and_oids_clear(&map);
 }
 
 struct commit_stack {
diff --git a/t/t5322-pack-objects-sparse.sh b/t/t5322-pack-objects-sparse.sh
index 30aef6498a..9f2a6e5d31 100755
--- a/t/t5322-pack-objects-sparse.sh
+++ b/t/t5322-pack-objects-sparse.sh
@@ -79,6 +79,9 @@ test_expect_success 'sparse pack-objects' '
 	test_cmp required_objects.txt sparse_required_objects.txt
 '
 
+# Demonstrate that the algorithms differ when we copy a tree wholesale
+# from one folder to another.
+
 test_expect_success 'duplicate a folder from f1 into f3' '
 	mkdir f3/f4 &&
 	cp -r f1/f1/* f3/f4 &&
@@ -95,7 +98,7 @@ test_expect_success 'duplicate a folder from f1 into f3' '
 '
 
 test_expect_success 'non-sparse pack-objects' '
-	git pack-objects --stdout --revs <packinput.txt >nonsparse.pack &&
+	git pack-objects --stdout --revs --no-sparse <packinput.txt >nonsparse.pack &&
 	git index-pack -o nonsparse.idx nonsparse.pack &&
 	git show-index <nonsparse.idx | awk "{print \$2}" >nonsparse_objects.txt &&
 	comm -1 -2 required_objects.txt nonsparse_objects.txt >nonsparse_required_objects.txt &&
@@ -103,11 +106,16 @@ test_expect_success 'non-sparse pack-objects' '
 '
 
 test_expect_success 'sparse pack-objects' '
+	git rev-parse			\
+		topic1			\
+		topic1^{tree}		\
+		topic1:f3		\
+		topic1:f3/f4		\
+		topic1:f3/f4/data.txt | sort >expect_sparse_objects.txt &&
 	git pack-objects --stdout --revs --sparse <packinput.txt >sparse.pack &&
 	git index-pack -o sparse.idx sparse.pack &&
 	git show-index <sparse.idx | awk "{print \$2}" >sparse_objects.txt &&
-	comm -1 -2 required_objects.txt sparse_objects.txt >sparse_required_objects.txt &&
-	test_cmp required_objects.txt sparse_required_objects.txt
+	test_cmp expect_sparse_objects.txt sparse_objects.txt
 '
 
 test_done