diff --git a/target/avr/helper.h b/target/avr/helper.h
index 8e1ae7fda0..4d02e648fa 100644
--- a/target/avr/helper.h
+++ b/target/avr/helper.h
@@ -19,10 +19,10 @@
  */
 
 DEF_HELPER_1(wdr, void, env)
-DEF_HELPER_1(debug, void, env)
-DEF_HELPER_1(break, void, env)
-DEF_HELPER_1(sleep, void, env)
-DEF_HELPER_1(unsupported, void, env)
+DEF_HELPER_1(debug, noreturn, env)
+DEF_HELPER_1(break, noreturn, env)
+DEF_HELPER_1(sleep, noreturn, env)
+DEF_HELPER_1(unsupported, noreturn, env)
 DEF_HELPER_3(outb, void, env, i32, i32)
 DEF_HELPER_2(inb, tl, env, i32)
 DEF_HELPER_3(fullwr, void, env, i32, i32)