diff --git a/mie/pass/pass-manager.c b/mie/pass/pass-manager.c
index 9e9458b..878badb 100644
--- a/mie/pass/pass-manager.c
+++ b/mie/pass/pass-manager.c
@@ -211,7 +211,10 @@ static void schedule_passes(
 		for (size_t i = 0; i < MIE_VECTOR_COUNT(pm->pm_nested); i++) {
 			struct mie_pass_manager *nested = pm->pm_nested.items[i];
 			struct mie_walk_item *item = mie_walker_get(&walker);
-			schedule_passes(nested, schedule, item->i_op, depth + 1);
+			if (item) {
+				schedule_passes(
+					nested, schedule, item->i_op, depth + 1);
+			}
 		}
 	} while (mie_walker_step(&walker) == MIE_SUCCESS);