diff --git a/ChangeLog b/ChangeLog
index 9f95e3bc27..afc94179bb 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sat Mar  9 21:25:45 2013  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
+
+	* file.c (rb_group_member): added an error check. SUS says,
+	  getgroups(small_value) may return EINVAL.
+
 Sat Mar  9 21:23:36 2013  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
 
 	* process.c (RB_MAX_GROUPS): moved to
diff --git a/file.c b/file.c
index 7d53f8d98f..44c019d7ae 100644
--- a/file.c
+++ b/file.c
@@ -1036,7 +1036,7 @@ rb_group_member(GETGROUPS_T gid)
     while (groups <= RB_MAX_GROUPS) {
 	gary = ALLOCV_N(GETGROUPS_T, v, groups);
 	anum = getgroups(groups, gary);
-	if (anum != groups)
+	if (anum != -1 && anum != groups)
 	    break;
 	groups *= 2;
 	if (v) {
@@ -1044,6 +1044,8 @@ rb_group_member(GETGROUPS_T gid)
 	    v = 0;
 	}
     }
+    if (anum == -1)
+	return FALSE;
 
     while (--anum >= 0) {
 	if (gary[anum] == gid) {
diff --git a/version.h b/version.h
index b97bf507c0..cd112921ff 100644
--- a/version.h
+++ b/version.h
@@ -1,6 +1,6 @@
 #define RUBY_VERSION "2.0.0"
 #define RUBY_RELEASE_DATE "2013-03-09"
-#define RUBY_PATCHLEVEL 22
+#define RUBY_PATCHLEVEL 23
 
 #define RUBY_RELEASE_YEAR 2013
 #define RUBY_RELEASE_MONTH 3