diff --git a/ChangeLog b/ChangeLog
index b32b1a98f5..fffcc76a81 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri Nov 22 22:30:00 2013  Kenta Murata  <mrkn@mrkn.jp>
+
+	* ext/bigdecimal/bigdecimal.c (BigDecimal_power):
+	  Round the result value only if the precision is given.
+
 Fri Nov 22 17:20:50 2013  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* transcode.c (str_transcode0): don't scrub invalid chars if
diff --git a/ext/bigdecimal/bigdecimal.c b/ext/bigdecimal/bigdecimal.c
index 0ed5147c9d..f630c0a167 100644
--- a/ext/bigdecimal/bigdecimal.c
+++ b/ext/bigdecimal/bigdecimal.c
@@ -2383,7 +2383,7 @@ retry:
 	GUARD_OBJ(y, VpCreateRbObject(1, "0"));
     }
     VpPower(y, x, int_exp);
-    if (VpIsDef(y)) {
+    if (!NIL_P(prec) && VpIsDef(y)) {
 	VpMidRound(y, VpGetRoundMode(), n);
     }
     return ToValue(y);