diff --git a/include/picrin.h b/include/picrin.h
index 792c8a04..8b11b64f 100644
--- a/include/picrin.h
+++ b/include/picrin.h
@@ -7,11 +7,19 @@
 #include "picconf.h"
 #include "picrin/value.h"
 
+typedef struct pic_callinfo {
+  struct pic_proc *proc;
+  int argc;
+} pic_callinfo;
+
 typedef struct {
   pic_value *sp;
   pic_value *stbase, *stend;
 
   pic_value sDEFINE, sCONS;
+  pic_callinfo *ci;
+  pic_callinfo *cibase, *ciend;
+
   pic_value sADD, sSUB, sMUL, sDIV;
   struct pic_env *global_env;
 
diff --git a/src/state.c b/src/state.c
index 3e7b1565..a59ddac2 100644
--- a/src/state.c
+++ b/src/state.c
@@ -29,6 +29,10 @@ pic_open()
   pic->stbase = pic->sp = (pic_value *)malloc(sizeof(pic_value) * PIC_STACK_SIZE);
   pic->stend = pic->stbase + PIC_STACK_SIZE;
 
+  /* callinfo */
+  pic->cibase = pic->ci = (pic_callinfo *)malloc(sizeof(pic_callinfo) * PIC_STACK_SIZE);
+  pic->ciend = pic->ciend + PIC_STACK_SIZE;
+
   /* memory heap */
   pic->heap = (struct heap_page *)malloc(sizeof(struct heap_page));
   init_heap_page(pic->heap);
diff --git a/src/vm.c b/src/vm.c
index 75178ebf..664cfe1a 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -317,6 +317,9 @@ pic_codegen(pic_state *pic, pic_value obj, struct pic_env *env)
 #define PUSH(v) (*pic->sp++ = (v))
 #define POP() (*--pic->sp)
 
+#define PUSHCI() (++pic->ci)
+#define POPCI() (pic->ci--)
+
 pic_value
 pic_run(pic_state *pic, struct pic_proc *proc, pic_value args)
 {
@@ -324,6 +327,8 @@ pic_run(pic_state *pic, struct pic_proc *proc, pic_value args)
   int ai = pic_gc_arena_preserve(pic);
 
   pc = proc->u.irep->code;
+  pic->ci->proc = proc;
+  pic->ci->argc = 0;
 
   VM_LOOP {
     CASE(OP_PUSHNIL) {
@@ -349,12 +354,17 @@ pic_run(pic_state *pic, struct pic_proc *proc, pic_value args)
     CASE(OP_CALL) {
       pic_value c;
       struct pic_proc *proc;
+      pic_callinfo *ci;
       int ai = pic_gc_arena_preserve(pic);
 
       pic_gc_protect(pic, c = POP());
       proc = pic_proc_ptr(c);
+      ci = PUSHCI();
+      ci->proc = proc;
+      ci->argc = pc->u.i;
       PUSH(proc->u.cfunc(pic));
       pic_gc_arena_restore(pic, ai);
+      POPCI();
       NEXT;
     }
     CASE(OP_CONS) {