diff --git a/include/cyclone/runtime.h b/include/cyclone/runtime.h
index 8e9b8193..e857b586 100644
--- a/include/cyclone/runtime.h
+++ b/include/cyclone/runtime.h
@@ -41,7 +41,8 @@ extern const object Cyc_EOF;
 
 object cell_get(object cell);
 
-#define global_set(glo,value) (glo=value)
+#define global_set(glo,value) Cyc_global_set(data, (object *)&glo, value)
+object Cyc_global_set(void *thd, object *glo, object value);
 
 /* Variable argument count support 
 
diff --git a/runtime.c b/runtime.c
index 4f7c18d5..840fc374 100644
--- a/runtime.c
+++ b/runtime.c
@@ -12,6 +12,16 @@
 //int JAE_DEBUG = 0;
 //int gcMoveCountsDEBUG[20] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
 
+TODO: still not good enough, need to be smarter when marking grey objs that are
+still on the stack (??). see reg-port in read.sld
+
+object Cyc_global_set(void *thd, object *glo, object value)
+{
+  gc_mut_update((gc_thread_data *)thd, *glo, value);
+  *(glo) = value;
+  return value;
+}
+
 /* Error checking section - type mismatch, num args, etc */
 /* Type names to use for error messages */
 const char *tag_names[21] = { \