diff --git a/tests/am-tests/src/tests/intr.c b/tests/am-tests/src/tests/intr.c
index e03a0a7..841e96b 100644
--- a/tests/am-tests/src/tests/intr.c
+++ b/tests/am-tests/src/tests/intr.c
@@ -3,11 +3,11 @@
 Context *simple_trap(Event ev, Context *ctx) {
   switch(ev.event) {
     case EVENT_IRQ_TIMER:
-      printf("t"); break;
+      putch('t'); break;
     case EVENT_IRQ_IODEV:
-      printf("d"); break;
+      putch('d'); break;
     case EVENT_YIELD:
-      printf("y"); break;
+      putch('y'); break;
     default:
       break;
   }