diff --git a/oss-fuzz/fuzz-commit-graph.c b/oss-fuzz/fuzz-commit-graph.c
index fe15e2c225..75e668a057 100644
--- a/oss-fuzz/fuzz-commit-graph.c
+++ b/oss-fuzz/fuzz-commit-graph.c
@@ -19,6 +19,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
 	 * touching the disk to keep the individual fuzz-test cases as fast as
 	 * possible.
 	 */
+	repo_set_hash_algo(the_repository, GIT_HASH_SHA1);
 	the_repository->settings.commit_graph_generation_version = 2;
 	the_repository->settings.commit_graph_read_changed_paths = 1;
 	g = parse_commit_graph(&the_repository->settings, (void *)data, size);