diff --git a/builtin/clean.c b/builtin/clean.c
index d0ec5e9963917f..92ad3148b4f5c1 100644
--- a/builtin/clean.c
+++ b/builtin/clean.c
@@ -1010,6 +1010,9 @@ int cmd_clean(int argc, const char **argv, const char *prefix)
 		dir.flags |= DIR_KEEP_UNTRACKED_CONTENTS;
 	}
 
+	prepare_repo_settings(the_repository);
+	the_repository->settings.command_requires_full_index = 0;
+
 	if (read_cache() < 0)
 		die(_("index file corrupt"));
 	enable_fscache(active_nr);
diff --git a/builtin/stash.c b/builtin/stash.c
index 9647b29efe8680..b54bccdd065f40 100644
--- a/builtin/stash.c
+++ b/builtin/stash.c
@@ -350,7 +350,7 @@ static int restore_untracked(struct object_id *u_tree)
 
 	child_process_init(&cp);
 	cp.git_cmd = 1;
-	strvec_pushl(&cp.args, "checkout-index", "--all", NULL);
+	strvec_pushl(&cp.args, "checkout-index", "--all", "--sparse", NULL);
 	strvec_pushf(&cp.env_array, "GIT_INDEX_FILE=%s",
 		     stash_index_path.buf);
 
diff --git a/t/perf/p2000-sparse-operations.sh b/t/perf/p2000-sparse-operations.sh
index 92a2fbdfbf9e37..1259d22222b5cd 100755
--- a/t/perf/p2000-sparse-operations.sh
+++ b/t/perf/p2000-sparse-operations.sh
@@ -107,6 +107,7 @@ test_perf_on_all () {
 
 test_perf_on_all git status
 test_perf_on_all 'git stash && git stash pop'
+test_perf_on_all 'echo >>new && git stash -u && git stash pop'
 test_perf_on_all git add -A
 test_perf_on_all git add .
 test_perf_on_all git commit -a -m A
diff --git a/t/t1092-sparse-checkout-compatibility.sh b/t/t1092-sparse-checkout-compatibility.sh
index 508cf99187d82b..bd2e54f259e545 100755
--- a/t/t1092-sparse-checkout-compatibility.sh
+++ b/t/t1092-sparse-checkout-compatibility.sh
@@ -1068,23 +1068,42 @@ test_expect_success 'clean' '
 	test_all_match git commit -m "ignore bogus files" &&
 
 	run_on_sparse mkdir folder1 &&
+	run_on_all mkdir -p deep/untracked-deep &&
 	run_on_all touch folder1/bogus &&
+	run_on_all touch folder1/untracked &&
+	run_on_all touch deep/untracked-deep/bogus &&
+	run_on_all touch deep/untracked-deep/untracked &&
 
 	test_all_match git status --porcelain=v2 &&
 	test_all_match git clean -f &&
 	test_all_match git status --porcelain=v2 &&
 	test_sparse_match ls &&
 	test_sparse_match ls folder1 &&
+	run_on_all test_path_exists folder1/bogus &&
+	run_on_all test_path_is_missing folder1/untracked &&
+	run_on_all test_path_exists deep/untracked-deep/bogus &&
+	run_on_all test_path_exists deep/untracked-deep/untracked &&
+
+	test_all_match git clean -fd &&
+	test_all_match git status --porcelain=v2 &&
+	test_sparse_match ls &&
+	test_sparse_match ls folder1 &&
+	run_on_all test_path_exists folder1/bogus &&
+	run_on_all test_path_exists deep/untracked-deep/bogus &&
+	run_on_all test_path_is_missing deep/untracked-deep/untracked &&
 
 	test_all_match git clean -xf &&
 	test_all_match git status --porcelain=v2 &&
 	test_sparse_match ls &&
 	test_sparse_match ls folder1 &&
+	run_on_all test_path_is_missing folder1/bogus &&
+	run_on_all test_path_exists deep/untracked-deep/bogus &&
 
 	test_all_match git clean -xdf &&
 	test_all_match git status --porcelain=v2 &&
 	test_sparse_match ls &&
 	test_sparse_match ls folder1 &&
+	run_on_all test_path_is_missing deep/untracked-deep/bogus &&
 
 	test_sparse_match test_path_is_dir folder1
 '
@@ -1202,6 +1221,8 @@ test_expect_success 'sparse-index is not expanded' '
 	git -C sparse-index add README.md &&
 	ensure_not_expanded diff --staged &&
 
+	ensure_not_expanded clean -fd &&
+
 	ensure_not_expanded checkout -f update-deep &&
 	(
 		sane_unset GIT_TEST_MERGE_ALGORITHM &&
@@ -1280,6 +1301,46 @@ test_expect_success 'sparse index is not expanded: read-tree' '
 	ensure_not_expanded read-tree --prefix=deep/deeper2 -u deepest
 '
 
+# NEEDSWORK: although the full repository's index is _not_ expanded as part of
+# stash, a temporary index, which is _not_ sparse, is created when stashing and
+# applying a stash of untracked files. As a result, the test reports that it
+# finds an instance of `ensure_full_index`, but it does not carry with it the
+# performance implications of expanding the full repository index.
+test_expect_success 'sparse index is not expanded: stash -u' '
+	init_repos &&
+
+	mkdir -p sparse-index/folder1 &&
+	echo >>sparse-index/README.md &&
+	echo >>sparse-index/a &&
+	echo >>sparse-index/folder1/new &&
+
+	GIT_TRACE2_EVENT="$(pwd)/trace2.txt" GIT_TRACE2_EVENT_NESTING=10 \
+		git -C sparse-index stash -u &&
+	test_region index ensure_full_index trace2.txt &&
+
+	GIT_TRACE2_EVENT="$(pwd)/trace2.txt" GIT_TRACE2_EVENT_NESTING=10 \
+		git -C sparse-index stash pop &&
+	test_region index ensure_full_index trace2.txt
+'
+
+# NEEDSWORK: similar to `git add`, untracked files outside of the sparse
+# checkout definition are successfully stashed and unstashed.
+test_expect_success 'stash -u outside sparse checkout definition' '
+	init_repos &&
+
+	write_script edit-contents <<-\EOF &&
+	echo text >>$1
+	EOF
+
+	run_on_sparse mkdir -p folder1 &&
+	run_on_all ../edit-contents folder1/new &&
+	test_all_match git stash -u &&
+	test_all_match git status --porcelain=v2 &&
+
+	test_all_match git stash pop -q &&
+	test_all_match git status --porcelain=v2
+'
+
 # NEEDSWORK: a sparse-checkout behaves differently from a full checkout
 # in this scenario, but it shouldn't.
 test_expect_success 'reset mixed and checkout orphan' '