diff --git a/ChangeLog b/ChangeLog
index 1d78571868..133690733a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Aug  1 22:16:30 2010  Kenta Murata  <mrkn@mrkn.jp>
+
+	* ext/bigdecimal/bigdecimal.c (BigDecimal_hash): use rb_memhash and
+	  take care of negative finite numbers properly.
+
 Sun Aug  1 20:57:22 2010  Tanaka Akira  <akr@fsij.org>
 
 	* ext/pathname/pathname.c (path_realpath): Pathname#realpath translated
diff --git a/ext/bigdecimal/bigdecimal.c b/ext/bigdecimal/bigdecimal.c
index 146145ce41..239fe05a76 100644
--- a/ext/bigdecimal/bigdecimal.c
+++ b/ext/bigdecimal/bigdecimal.c
@@ -228,12 +228,9 @@ BigDecimal_hash(VALUE self)
     GUARD_OBJ(p,GetVpValue(self,1));
     hash = (U_LONG)p->sign;
     /* hash!=2: the case for 0(1),NaN(0) or +-Infinity(3) is sign itself */
-    if(hash==2) {
-        for(i = 0; i < p->Prec;i++) {
-            hash = 31 * hash + p->frac[i];
-            hash ^= p->frac[i];
-        }
-        hash += p->exponent;
+    if(hash == 2 || hash == -2) {
+	hash ^= rb_memhash(p->frac, sizeof(U_LONG)*p->Prec);
+	hash += p->exponent;
     }
     return INT2FIX(hash);
 }