diff --git a/extlib/benz/codegen.c b/extlib/benz/codegen.c
index d4f2c187..1cfa5f19 100644
--- a/extlib/benz/codegen.c
+++ b/extlib/benz/codegen.c
@@ -436,7 +436,7 @@ define_var(pic_state *pic, analyze_scope *scope, pic_sym *sym)
   int ret;
 
   if (search_scope(scope, sym)) {
-    if (scope->depth > 0 || (pic_dict_has(pic, pic->globals, sym) && ! pic_invalid_p(pic_box_ptr(pic_dict_ref(pic, pic->globals, sym))->value))) {
+    if (scope->depth > 0 || (pic_reg_has(pic, pic->globals, sym) && ! pic_invalid_p(pic_box_ptr(pic_reg_ref(pic, pic->globals, sym))->value))) {
       pic_warnf(pic, "redefining variable: ~s", pic_obj_value(sym));
     }
     return;
diff --git a/extlib/benz/gc.c b/extlib/benz/gc.c
index a7096cca..30c36bab 100644
--- a/extlib/benz/gc.c
+++ b/extlib/benz/gc.c
@@ -484,6 +484,7 @@ gc_mark_phase(pic_state *pic)
 
   M(uDEFINE); M(uLAMBDA); M(uIF); M(uBEGIN); M(uQUOTE); M(uSETBANG); M(uDEFINE_MACRO);
   M(uDEFINE_LIBRARY); M(uIMPORT); M(uEXPORT); M(uCOND_EXPAND);
+
   M(uCONS); M(uCAR); M(uCDR); M(uNILP); M(uSYMBOLP); M(uPAIRP);
   M(uADD); M(uSUB); M(uMUL); M(uDIV); M(uEQ); M(uLT); M(uLE); M(uGT); M(uGE); M(uNOT);
 
@@ -491,6 +492,9 @@ gc_mark_phase(pic_state *pic)
   P(pCONS); P(pCAR); P(pCDR); P(pNILP); P(pSYMBOLP); P(pPAIRP); P(pNOT);
   P(pADD); P(pSUB); P(pMUL); P(pDIV); P(pEQ); P(pLT); P(pLE); P(pGT); P(pGE);
 
+  M(cCONS); M(cCAR); M(cCDR); M(cNILP); M(cSYMBOLP); M(cPAIRP); M(cNOT);
+  M(cADD); M(cSUB); M(cMUL); M(cDIV); M(cEQ); M(cLT); M(cLE); M(cGT); M(cGE);
+
   /* global variables */
   if (pic->globals) {
     gc_mark_object(pic, (union object *)pic->globals);
diff --git a/extlib/benz/include/picrin.h b/extlib/benz/include/picrin.h
index 50737ea3..f4ef47db 100644
--- a/extlib/benz/include/picrin.h
+++ b/extlib/benz/include/picrin.h
@@ -119,7 +119,7 @@ struct pic_state {
 
   khash_t(s) syms;              /* name to symbol */
   int ucnt;
-  struct pic_dict *globals;
+  struct pic_reg *globals;
   struct pic_dict *macros;
   pic_value libs;
   struct pic_reg *attrs;
diff --git a/extlib/benz/state.c b/extlib/benz/state.c
index 86f3d88a..3cd3c895 100644
--- a/extlib/benz/state.c
+++ b/extlib/benz/state.c
@@ -407,7 +407,7 @@ pic_open(pic_allocf allocf, void *userdata)
   pic->pGE = pic_invalid_value();
 
   /* root tables */
-  pic->globals = pic_make_dict(pic);
+  pic->globals = pic_make_reg(pic);
   pic->macros = pic_make_dict(pic);
   pic->attrs = pic_make_reg(pic);
 
diff --git a/extlib/benz/vm.c b/extlib/benz/vm.c
index 2f291111..dda6de12 100644
--- a/extlib/benz/vm.c
+++ b/extlib/benz/vm.c
@@ -387,15 +387,15 @@ pic_get_args(pic_state *pic, const char *format, ...)
 }
 
 struct pic_box *
-pic_vm_gref_slot(pic_state *pic, pic_sym *uid)
+pic_vm_gref_slot(pic_state *pic, pic_sym *uid) /* TODO: make this static */
 {
   struct pic_box *box;
 
-  if (pic_dict_has(pic, pic->globals, uid)) {
-    return pic_box_ptr(pic_dict_ref(pic, pic->globals, uid));
+  if (pic_reg_has(pic, pic->globals, uid)) {
+    return pic_box_ptr(pic_reg_ref(pic, pic->globals, uid));
   }
   box = pic_box(pic, pic_invalid_value());
-  pic_dict_set(pic, pic->globals, uid, pic_obj_value(box));
+  pic_reg_set(pic, pic->globals, uid, pic_obj_value(box));
   return box;
 }
 
@@ -1112,7 +1112,7 @@ pic_define_(pic_state *pic, const char *name, pic_value val)
   if ((uid = pic_find_variable(pic, pic->lib->env, pic_obj_value(sym))) == NULL) {
     uid = pic_add_variable(pic, pic->lib->env, pic_obj_value(sym));
   } else {
-    if (pic_dict_has(pic, pic->globals, uid)) {
+    if (pic_reg_has(pic, pic->globals, uid)) {
       pic_warnf(pic, "redefining variable: ~s", pic_obj_value(uid));
     }
   }