diff --git a/ChangeLog b/ChangeLog
index 0997df6c77..5492202994 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Mon Jul 16 15:37:56 2012  Tanaka Akira  <akr@fsij.org>
+
+	* bignum.c (rb_big_eq): use rb_big_float_cmp.
+
 Mon Jul 16 15:00:45 2012  Tanaka Akira  <akr@fsij.org>
 
 	* internal.h (rb_big_float_cmp): declared.
diff --git a/bignum.c b/bignum.c
index 839a866ae9..592c8f88ce 100644
--- a/bignum.c
+++ b/bignum.c
@@ -1616,14 +1616,7 @@ rb_big_eq(VALUE x, VALUE y)
       case T_BIGNUM:
 	break;
       case T_FLOAT:
-	{
-	    volatile double a, b;
-
-	    a = RFLOAT_VALUE(y);
-	    if (isnan(a) || isinf(a)) return Qfalse;
-	    b = rb_big2dbl(x);
-	    return (a == b)?Qtrue:Qfalse;
-	}
+        return rb_big_float_cmp(x, y) == INT2FIX(0) ? Qtrue : Qfalse;
       default:
 	return rb_equal(y, x);
     }