diff --git a/builtin/diff.c b/builtin/diff.c
index dd8ce688ba7054..a02c5b8ed95021 100644
--- a/builtin/diff.c
+++ b/builtin/diff.c
@@ -436,6 +436,9 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 	}
 
 	prefix = setup_git_directory_gently(&nongit);
+	
+	prepare_repo_settings(the_repository);
+	the_repository->settings.command_requires_full_index = 0;
 
 	if (!no_index) {
 		/*
diff --git a/t/t1092-sparse-checkout-compatibility.sh b/t/t1092-sparse-checkout-compatibility.sh
index 0dfffb8856f466..4a3e7eecc28f4e 100755
--- a/t/t1092-sparse-checkout-compatibility.sh
+++ b/t/t1092-sparse-checkout-compatibility.sh
@@ -693,6 +693,11 @@ test_expect_success 'sparse-index is not expanded' '
 	echo >>sparse-index/untracked.txt &&
 	ensure_not_expanded add . &&
 
+	echo "a test change" >> sparse-index/README.md &&
+	ensure_not_expanded diff &&
+	git -C sparse-index add README.md &&
+	ensure_not_expanded diff --staged &&
+
 	ensure_not_expanded checkout -f update-deep &&
 	(
 		sane_unset GIT_TEST_MERGE_ALGORITHM &&