diff --git a/include/mruby/internal.h b/include/mruby/internal.h
index 86883f821..02500521b 100644
--- a/include/mruby/internal.h
+++ b/include/mruby/internal.h
@@ -79,8 +79,8 @@ mrb_int mrb_div_int(mrb_int x, mrb_int y);
 mrb_value mrb_int_add(mrb_state *mrb, mrb_value x, mrb_value y);
 mrb_value mrb_int_sub(mrb_state *mrb, mrb_value x, mrb_value y);
 mrb_value mrb_int_mul(mrb_state *mrb, mrb_value x, mrb_value y);
-void mrb_int_zerodiv(mrb_state *mrb);
-void mrb_int_overflow(mrb_state *mrb, const char *reason);
+mrb_noreturn void mrb_int_zerodiv(mrb_state *mrb);
+mrb_noreturn void mrb_int_overflow(mrb_state *mrb, const char *reason);
 
 #ifdef MRB_USE_COMPLEX
 mrb_value mrb_complex_new(mrb_state *mrb, mrb_float x, mrb_float y);
diff --git a/src/numeric.c b/src/numeric.c
index 90fb58c2d..7d2b3a8b4 100644
--- a/src/numeric.c
+++ b/src/numeric.c
@@ -21,13 +21,13 @@
 #endif
 #endif
 
-void
+mrb_noreturn void
 mrb_int_overflow(mrb_state *mrb, const char *reason)
 {
   mrb_raisef(mrb, E_RANGE_ERROR, "integer overflow in %s", reason);
 }
 
-void
+mrb_noreturn void
 mrb_int_zerodiv(mrb_state *mrb)
 {
   mrb_raise(mrb, E_ZERODIV_ERROR, "divided by 0");