diff --git a/ChangeLog b/ChangeLog
index 66d256bdd6..6c6c9bb7be 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Wed Jul 16 16:23:58 2003  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* eval.c (rb_proc_new): call svalue_to_avalue for yield argument.
+
 Wed Jul 16 00:31:00 2003  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* eval.c (rb_disable_super, rb_enable_super): deprecate.
diff --git a/eval.c b/eval.c
index 4a3850c0e6..820b1ca5c4 100644
--- a/eval.c
+++ b/eval.c
@@ -7553,12 +7553,29 @@ bmcall(args, method)
     return method_call(RARRAY(a)->len, RARRAY(a)->ptr, method);
 }
 
+struct proc_funcall_data {
+    VALUE (*func)(ANYARGS);
+    VALUE val;
+};
+
+static VALUE
+proc_funcall(args, data)
+    VALUE args;
+    struct proc_funcall_data *data;
+{
+    return (*data->func)(svalue_to_avalue(args), data->val);
+}
+
 VALUE
 rb_proc_new(func, val)
     VALUE (*func)(ANYARGS);	/* VALUE yieldarg[, VALUE procarg] */
     VALUE val;
 {
-    return rb_iterate((VALUE(*)_((VALUE)))mproc, 0, func, val);
+    struct proc_funcall_data data;
+
+    data.func = func;
+    data.val = val;
+    return rb_iterate((VALUE(*)_((VALUE)))mproc, 0, proc_funcall, (VALUE)&data);
 }
 
 static VALUE
@@ -9256,6 +9273,11 @@ rb_thread_start_0(fn, arg, th_arg)
     enum thread_status status;
     int state;
 
+    if (OBJ_FROZEN(curr_thread->thgroup)) {
+	rb_raise(rb_eThreadError, 
+		 "can't start a new thread (frozen ThreadGroup)");
+    }
+
 #if defined(HAVE_SETITIMER)
     if (!thread_init) {
 #ifdef POSIX_SIGNAL