diff --git a/repo-settings.c b/repo-settings.c
index ada638fd58573c..4e673f66f5b823 100644
--- a/repo-settings.c
+++ b/repo-settings.c
@@ -70,7 +70,7 @@ void prepare_repo_settings(struct repository *r)
 	repo_cfg_bool(r, "fetch.writecommitgraph", &r->settings.fetch_write_commit_graph, 0);
 	repo_cfg_bool(r, "pack.usesparse", &r->settings.pack_use_sparse, 1);
 	repo_cfg_bool(r, "core.multipackindex", &r->settings.core_multi_pack_index, 1);
-	repo_cfg_bool(r, "index.sparse", &r->settings.sparse_index, 0);
+	repo_cfg_bool(r, "index.sparse", &r->settings.sparse_index, 1);
 
 	/*
 	 * The GIT_TEST_MULTI_PACK_INDEX variable is special in that
diff --git a/sparse-index.c b/sparse-index.c
index 7b7ff79e0443a8..a6c65082e857cd 100644
--- a/sparse-index.c
+++ b/sparse-index.c
@@ -103,7 +103,7 @@ int set_sparse_index_config(struct repository *repo, int enable)
 	char *config_path = repo_git_path(repo, "config.worktree");
 	res = git_config_set_in_file_gently(config_path,
 					    "index.sparse",
-					    enable ? "true" : NULL);
+					    enable ? "true" : "false");
 	free(config_path);
 
 	prepare_repo_settings(repo);
diff --git a/t/t1091-sparse-checkout-builtin.sh b/t/t1091-sparse-checkout-builtin.sh
index ef14f659668f6c..8f54e69502e2be 100755
--- a/t/t1091-sparse-checkout-builtin.sh
+++ b/t/t1091-sparse-checkout-builtin.sh
@@ -219,7 +219,7 @@ test_expect_success 'sparse-index enabled and disabled' '
 		test-tool -C repo read-cache --table >cache &&
 		! grep " tree " cache &&
 		git -C repo config --list >config &&
-		! grep index.sparse config
+		test_cmp_config -C repo false index.sparse
 	)
 '
 
diff --git a/t/t1092-sparse-checkout-compatibility.sh b/t/t1092-sparse-checkout-compatibility.sh
index 8943bd5e699630..71daf2d87609d2 100755
--- a/t/t1092-sparse-checkout-compatibility.sh
+++ b/t/t1092-sparse-checkout-compatibility.sh
@@ -147,6 +147,7 @@ init_repos () {
 	git -C sparse-index reset --hard &&
 
 	# initialize sparse-checkout definitions
+	git -C sparse-checkout config index.sparse false &&
 	git -C sparse-checkout sparse-checkout init --cone &&
 	git -C sparse-checkout sparse-checkout set deep &&
 	git -C sparse-index sparse-checkout init --cone --sparse-index &&
diff --git a/t/t7817-grep-sparse-checkout.sh b/t/t7817-grep-sparse-checkout.sh
index 590b99bbb6f7bb..547bae48619c12 100755
--- a/t/t7817-grep-sparse-checkout.sh
+++ b/t/t7817-grep-sparse-checkout.sh
@@ -49,7 +49,7 @@ test_expect_success 'setup' '
 		echo "text" >B/b &&
 		git add A B &&
 		git commit -m sub &&
-		git sparse-checkout init --cone &&
+		git sparse-checkout init --cone --no-sparse-index &&
 		git sparse-checkout set B
 	) &&