diff --git a/ChangeLog b/ChangeLog
index 7aa77950da..445d4443f3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Thu Jun 13 18:34:20 2013  Tanaka Akira  <akr@fsij.org>
+
+	* bignum.c (bigdivrem): Use nlz.
+
 Thu Jun 13 14:51:06 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* include/ruby/ruby.h (RUBY_SAFE_LEVEL_CHECK): check constant safe
diff --git a/bignum.c b/bignum.c
index 7086fe5724..42d0a74d6c 100644
--- a/bignum.c
+++ b/bignum.c
@@ -3793,12 +3793,9 @@ bigdivrem(VALUE x, VALUE y, volatile VALUE *divp, volatile VALUE *modp)
     if (nx==ny) zds[nx+1] = 0;
     while (!yds[ny-1]) ny--;
 
-    dd = 0;
     q = yds[ny-1];
-    while ((q & (BDIGIT)(1UL<<(BITSPERDIG-1))) == 0) {
-	q <<= 1UL;
-	dd++;
-    }
+    dd = nlz(q);
+    q <<= dd;
     if (dd) {
 	yy = rb_big_clone(y);
 	tds = BDIGITS(yy);