diff --git a/ChangeLog b/ChangeLog
index 66b253a7e6..0879053a4a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Jun 26 04:03:50 2007  Koichi Sasada  <ko1@atdot.net>
+
+	* insnhelper.ci (vm_yield_with_cfunc), proc.c: fix Method#to_proc
+	  to return lamba Proc ([ruby-dev:31021], [ruby-dev:31037]).
+
 Tue Jun 26 03:46:08 2007  Koichi Sasada  <ko1@atdot.net>
 
 	* cont.c (rb_fiber_s_new): fix to clear rb_thread_t#tag.
diff --git a/insnhelper.ci b/insnhelper.ci
index 5c25a0e0bf..eb228b4295 100644
--- a/insnhelper.ci
+++ b/insnhelper.ci
@@ -562,6 +562,20 @@ vm_call_method(rb_thread_t *th, rb_control_frame_t *cfp,
 
 /* yield */
 
+static inline int
+block_proc_is_lambda(VALUE procval)
+{
+    rb_proc_t *proc;
+
+    if (procval) {
+	GetProcPtr(procval, proc);
+	return proc->is_lambda;
+    }
+    else {
+	return 0;
+    }
+}
+
 static inline VALUE
 vm_yield_with_cfunc(rb_thread_t *th, rb_block_t *block,
 		    VALUE self, int argc, VALUE *argv)
@@ -569,15 +583,21 @@ vm_yield_with_cfunc(rb_thread_t *th, rb_block_t *block,
     NODE *ifunc = (NODE *) block->iseq;
     VALUE val;
     VALUE arg;
+    int lambda = block_proc_is_lambda(block->proc);
 
-    if (argc == 1) {
-	arg = *argv;
-    }
-    else if (argc > 1) {
+    if (lambda) {
 	arg = rb_ary_new4(argc, argv);
     }
     else {
-	arg = rb_ary_new();
+	if (argc == 1) {
+	    arg = *argv;
+	}
+	else if (argc > 1) {
+	    arg = rb_ary_new4(argc, argv);
+	}
+	else {
+	    arg = rb_ary_new();
+	}
     }
 
     vm_push_frame(th, 0, FRAME_MAGIC_IFUNC,
@@ -970,20 +990,6 @@ vm_search_super_klass(VALUE klass, VALUE recv)
     return klass;
 }
 
-static inline int
-block_proc_is_lambda(VALUE procval)
-{
-    rb_proc_t *proc;
-
-    if (procval) {
-	GetProcPtr(procval, proc);
-	return proc->is_lambda;
-    }
-    else {
-	return 0;
-    }
-}
-
 static void
 call_yarv_end_proc(VALUE data)
 {
diff --git a/proc.c b/proc.c
index 8d6ec0e8cd..59de71dd61 100644
--- a/proc.c
+++ b/proc.c
@@ -1312,10 +1312,17 @@ mproc(VALUE method)
     return rb_funcall(Qnil, rb_intern("proc"), 0);
 }
 
+static VALUE
+mlambda(VALUE method)
+{
+    return rb_funcall(Qnil, rb_intern("lambda"), 0);
+}
+
 static VALUE
 bmcall(VALUE args, VALUE method)
 {
     volatile VALUE a;
+
     if (CLASS_OF(args) != rb_cArray) {
 	args = rb_ary_new3(1, args);
     }
@@ -1356,7 +1363,7 @@ method_proc(VALUE method)
      *   end
      * end
      */
-    proc = rb_iterate((VALUE (*)(VALUE))mproc, 0, bmcall, method);
+    proc = rb_iterate((VALUE (*)(VALUE))mlambda, 0, bmcall, method);
     return proc;
 }