diff --git a/rational.c b/rational.c
index 1909536..cd03174 100644
--- a/rational.c
+++ b/rational.c
@@ -476,13 +476,12 @@ nurat_canonicalization(int f)
 }
 #endif
 
-inline static void
+inline static VALUE
 nurat_int_check(VALUE num)
 {
-    if (!(RB_TYPE_P(num, T_FIXNUM) || RB_TYPE_P(num, T_BIGNUM))) {
-	if (!k_numeric_p(num) || !f_integer_p(num))
-	    rb_raise(rb_eTypeError, "not an integer");
-    }
+    if (RB_TYPE_P(num, T_FIXNUM) || RB_TYPE_P(num, T_BIGNUM))
+	return num;
+    return rb_to_int(num);
 }
 
 inline static VALUE