diff --git a/include/picrin.h b/include/picrin.h
index 955dac01..6683dd8e 100644
--- a/include/picrin.h
+++ b/include/picrin.h
@@ -77,10 +77,6 @@ void pic_close(pic_state *);
 int pic_get_args(pic_state *, const char *, ...);
 void pic_defun(pic_state *, const char *, pic_func_t);
 
-bool pic_eq_p(pic_state *, pic_value, pic_value);
-bool pic_eqv_p(pic_state *, pic_value, pic_value);
-bool pic_equal_p(pic_state *, pic_value, pic_value);
-
 pic_sym pic_intern_cstr(pic_state *, const char *);
 const char *pic_symbol_name(pic_state *, pic_sym);
 
diff --git a/include/picrin/value.h b/include/picrin/value.h
index d72eb4f3..06e02c92 100644
--- a/include/picrin/value.h
+++ b/include/picrin/value.h
@@ -26,6 +26,7 @@ enum pic_vtype {
  *   sym   : 1111111111110111 0000000000000000 SSSSSSSSSSSSSSSS SSSSSSSSSSSSSSSS
  *   char  : 1111111111111000 0000000000000000 CCCCCCCCCCCCCCCC ................
  */
+
 typedef struct {
   union {
     void *data;
@@ -149,4 +150,7 @@ pic_value pic_char_value(char c);
 #define pic_str_p(v) (pic_type(v) == PIC_TT_STRING)
 #define pic_vec_p(v) (pic_type(v) == PIC_TT_VECTOR)
 
+bool pic_eq_p(pic_value, pic_value);
+bool pic_eqv_p(pic_value, pic_value);
+
 #endif
diff --git a/src/bool.c b/src/bool.c
index 3d319739..a5aaf294 100644
--- a/src/bool.c
+++ b/src/bool.c
@@ -2,22 +2,6 @@
 
 #include "picrin.h"
 
-bool
-pic_eq_p(pic_state *pic, pic_value x, pic_value y)
-{
-  if (pic_type(x) != pic_type(y))
-    return false;
-
-  switch (pic_type(x)) {
-  case PIC_TT_NIL:
-    return true;
-  case PIC_TT_SYMBOL:
-    return pic_sym(x) == pic_sym(y);
-  default:
-    return false;
-  }
-}
-
 static pic_value
 pic_bool_eq_p(pic_state *pic)
 {
@@ -25,7 +9,7 @@ pic_bool_eq_p(pic_state *pic)
 
   pic_get_args(pic, "oo", &x, &y);
 
-  return pic_bool_value(pic_eq_p(pic, x, y));
+  return pic_bool_value(pic_eq_p(x, y));
 }
 
 /* TODO: replace it with native opcode */
diff --git a/src/pair.c b/src/pair.c
index 231912cc..922a73bb 100644
--- a/src/pair.c
+++ b/src/pair.c
@@ -102,7 +102,7 @@ pic_assq(pic_state *pic, pic_value key, pic_value assoc)
     return assoc;
 
   cell = pic_car(pic, assoc);
-  if (pic_eq_p(pic, key, pic_car(pic, cell)))
+  if (pic_eq_p(key, pic_car(pic, cell)))
     return cell;
 
   assoc = pic_cdr(pic, assoc);
diff --git a/src/value.c b/src/value.c
index c63ff683..3b76bf67 100644
--- a/src/value.c
+++ b/src/value.c
@@ -216,3 +216,31 @@ pic_undef_value()
   pic_init_value(v, PIC_VTYPE_UNDEF);
   return v;
 }
+
+#if PIC_NAN_BOXING
+
+bool
+pic_eq_p(pic_value x, pic_value y)
+{
+  return x.u.data == y.u.data;
+}
+
+#else
+
+bool
+pic_eq_p(pic_value x, pic_value y)
+{
+  if (pic_type(x) != pic_type(y))
+    return false;
+
+  switch (pic_type(x)) {
+  case PIC_TT_NIL:
+    return true;
+  case PIC_TT_SYMBOL:
+    return pic_sym(x) == pic_sym(y);
+  default:
+    return false;
+  }
+}
+
+#endif