diff --git a/mrbgems/mruby-cmath/src/cmath.c b/mrbgems/mruby-cmath/src/cmath.c
index de59adf96..3433c23a6 100644
--- a/mrbgems/mruby-cmath/src/cmath.c
+++ b/mrbgems/mruby-cmath/src/cmath.c
@@ -33,7 +33,7 @@ cmath_get_complex(mrb_state *mrb, mrb_value c, mrb_float *r, mrb_float *i)
     *i = 0;
     return FALSE;
   }
-  else if (mrb_obj_is_kind_of(mrb, c, mrb_class_get(mrb, "Complex"))) {
+  else if (mrb_type(c) == MRB_TT_COMPLEX) {
     mrb_complex_get(mrb, c, r, i);
     return TRUE;
   }
diff --git a/src/error.c b/src/error.c
index c40ea75c9..9bbb34c83 100644
--- a/src/error.c
+++ b/src/error.c
@@ -208,7 +208,7 @@ mrb_exc_raise(mrb_state *mrb, mrb_value exc)
     mrb->exc = mrb_obj_ptr(exc);
   }
   else {
-    if (!mrb_obj_is_kind_of(mrb, exc, E_EXCEPTION)) {
+    if (mrb_type(exc) != MRB_TT_EXCEPTION) {
       mrb_raise(mrb, E_TYPE_ERROR, "exception object expected");
     }
     mrb_exc_set(mrb, exc);
@@ -499,7 +499,7 @@ exception_call:
       break;
   }
   if (argc > 0) {
-    if (!mrb_obj_is_kind_of(mrb, mesg, E_EXCEPTION))
+    if (mrb_type(mesg) != MRB_TT_EXCEPTION)
       mrb_raise(mrb, E_EXCEPTION, "exception object expected");
     if (argc > 2)
       set_backtrace(mrb, mesg, argv[2]);
diff --git a/src/range.c b/src/range.c
index 84855cfcf..fc126be80 100644
--- a/src/range.c
+++ b/src/range.c
@@ -311,7 +311,6 @@ range_eql(mrb_state *mrb, mrb_value range)
   struct RRange *r, *o;
 
   if (mrb_obj_equal(mrb, range, obj)) return mrb_true_value();
-  if (!mrb_obj_is_kind_of(mrb, obj, mrb->range_class)) return mrb_false_value();
   if (!mrb_range_p(obj)) return mrb_false_value();
 
   r = mrb_range_ptr(mrb, range);