diff --git a/ChangeLog b/ChangeLog
index 46747c1300..4da000a17e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Feb  8 01:00:21 2011  CHIKANAGA Tomoyuki  <nagachika00@gmail.com>
+
+	* process.c (proc_setgroups): add GC guard to prevent intermediate
+	  variable from GC.
+
 Tue Feb  8 00:56:33 2011  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* misc/ruby-mode.el (ruby-expr-beg, ruby-in-here-doc-p): tell
diff --git a/process.c b/process.c
index f957d24613..df0350e3f2 100644
--- a/process.c
+++ b/process.c
@@ -4608,9 +4608,11 @@ proc_setgroups(VALUE obj, VALUE ary)
 	    }
 	    else {
 		gr = getgrnam(RSTRING_PTR(tmp));
-		if (gr == NULL)
+		if (gr == NULL) {
+		    RB_GC_GUARD(tmp);
 		    rb_raise(rb_eArgError,
 			     "can't find group for %s", RSTRING_PTR(tmp));
+		}
 		groups[i] = gr->gr_gid;
 	    }
 	}