diff --git a/ChangeLog b/ChangeLog
index a2ed59c99e..359bd95eec 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Mon May  2 06:58:38 2016  Tanaka Akira  <akr@fsij.org>
+
+	* complex.c: Don't refer rb_cFixnum and rb_cBignum.
+	  (k_fixnum_p): Use FIXNUM_P.
+	  (k_bignum_p): Use RB_TYPE_P.
+
 Mon May  2 01:27:59 2016  Tanaka Akira  <akr@fsij.org>
 
 	* test/ruby/test_numeric.rb (test_step): Use Integer::FIXNUM_MAX.
diff --git a/complex.c b/complex.c
index 357e53c865..0d4073018d 100644
--- a/complex.c
+++ b/complex.c
@@ -238,13 +238,13 @@ k_numeric_p(VALUE x)
 inline static VALUE
 k_fixnum_p(VALUE x)
 {
-    return f_kind_of_p(x, rb_cFixnum);
+    return FIXNUM_P(x);
 }
 
 inline static VALUE
 k_bignum_p(VALUE x)
 {
-    return f_kind_of_p(x, rb_cBignum);
+    return RB_TYPE_P(x, T_BIGNUM);
 }
 
 inline static VALUE