diff --git a/include/cyclone/runtime.h b/include/cyclone/runtime.h
index be43abf7..69492d23 100644
--- a/include/cyclone/runtime.h
+++ b/include/cyclone/runtime.h
@@ -200,7 +200,7 @@ object Cyc_command_line_arguments(void *data, object cont);
 object Cyc_system(object cmd);
 object Cyc_char2integer(object chr);
 object Cyc_integer2char(void *data, object n);
-void Cyc_halt(closure);
+void Cyc_halt(object obj);
 object __halt(object obj);
 port_type Cyc_stdout(void);
 port_type Cyc_stdin(void);
diff --git a/runtime.c b/runtime.c
index 9d929b68..84c7f463 100644
--- a/runtime.c
+++ b/runtime.c
@@ -1935,9 +1935,7 @@ object Cyc_integer2char(void *data, object n)
   return obj_char2obj(val);
 }
 
-void Cyc_halt(closure);
-void Cyc_halt(env)
-closure env;
+void Cyc_halt(object obj)
 {
 #if DEBUG_SHOW_DIAG
   gc_print_stats(Cyc_heap);