diff --git a/ChangeLog b/ChangeLog
index b51a4050e6..ef3593b8df 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Feb  7 03:01:46 2010  Tanaka Akira  <akr@fsij.org>
+
+	* math.c (math_lgamma): initialize sign because
+	  lgamma(NaN) doesn't set the sign in OpenSolaris.
+
 Sun Feb  7 00:23:21 2010  Shugo Maeda  <shugo@ruby-lang.org>
 
 	* class.c (rb_class_init_copy): raise a TypeError if the argument is 
diff --git a/math.c b/math.c
index 1d7d5e4188..027932dee9 100644
--- a/math.c
+++ b/math.c
@@ -710,7 +710,7 @@ static VALUE
 math_lgamma(VALUE obj, VALUE x)
 {
     double d0, d;
-    int sign;
+    int sign=1;
     VALUE v;
     Need_Float(x);
     errno = 0;