diff --git a/ChangeLog b/ChangeLog
index 09f4763cdb..a61ff61c9f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Sat Jun 18 02:36:00 2011  Kenta Murata  <mrkn@mrkn.jp>
+
+	* ext/bigdecimal/bigdecimal.c (VpNewRbClass): fix type of the 2nd
+	  argument.
+
+	* ext/bigdecimal/bigdecimal.h: ditto.
+
 Sat Jun 18 02:30:00 2011  Kenta Murata  <mrkn@mrkn.jp>
 
 	* ext/bigdecimal/bigdecimal.c (BigMath_s_exp): move BigMath.exp from
diff --git a/ext/bigdecimal/bigdecimal.c b/ext/bigdecimal/bigdecimal.c
index 4fc22b51ce..9e22dc55e1 100644
--- a/ext/bigdecimal/bigdecimal.c
+++ b/ext/bigdecimal/bigdecimal.c
@@ -487,7 +487,7 @@ GetPositiveInt(VALUE v)
 }
 
 VP_EXPORT Real *
-VpNewRbClass(size_t mx, char *str, VALUE klass)
+VpNewRbClass(size_t mx, const char *str, VALUE klass)
 {
     Real *pv = VpAlloc(mx,str);
     pv->obj = TypedData_Wrap_Struct(klass, &BigDecimal_data_type, pv);
diff --git a/ext/bigdecimal/bigdecimal.h b/ext/bigdecimal/bigdecimal.h
index b086c68c17..d6a3f337c6 100644
--- a/ext/bigdecimal/bigdecimal.h
+++ b/ext/bigdecimal/bigdecimal.h
@@ -154,7 +154,7 @@ typedef struct {
  */
 
 VP_EXPORT  Real *
-VpNewRbClass(size_t mx, char *str, VALUE klass);
+VpNewRbClass(size_t mx, char const *str, VALUE klass);
 
 VP_EXPORT  Real *VpCreateRbObject(size_t mx,const char *str);