diff --git a/ChangeLog b/ChangeLog
index e87b49bf8e..3a04fb1231 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Mon May 21 15:02:37 2012  Akinori MUSHA  <knu@iDaemons.org>
+
+	* ext/syslog/syslog.c (mSyslog_inspect): Make sure self is a
+	  module before calling rb_class2name().
+
 Mon May 21 12:44:11 2012  URABE Shyouhei  <shyouhei@ruby-lang.org>
 
 	* .travis.yml (install): It seems tcl/tk is skipped in Travis
diff --git a/ext/syslog/syslog.c b/ext/syslog/syslog.c
index f4c45dfbe4..a0b3ed3af7 100644
--- a/ext/syslog/syslog.c
+++ b/ext/syslog/syslog.c
@@ -315,6 +315,8 @@ static VALUE mSyslog_inspect(VALUE self)
 {
     char buf[1024];
 
+    Check_Type(self, T_MODULE);
+
     if (syslog_opened) {
 	snprintf(buf, sizeof(buf),
 	  "<#%s: opened=true, ident=\"%s\", options=%d, facility=%d, mask=%d>",