diff --git a/ChangeLog b/ChangeLog
index d68a07f40f..272660284e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+Sat Jul  7 15:30:05 2007  Koichi Sasada  <ko1@atdot.net>
+
+	* insnhelper.ci (vm_yield_setup_args), vm.c, insns.def: 
+	  fix to pass nil as block parameter to yielded block.
+	  [ruby-dev:31147]
+
+	* bootstraptest/test_block.rb: add a test for above.
+
 Fri Jul  6 19:55:10 2007  Keiju Ishitsuka  <keiju@ruby-lang.org>
 
 	* lib/irb.rb: typo. Thanks, Giles Bowkett.
diff --git a/bootstraptest/test_block.rb b/bootstraptest/test_block.rb
index e20f5937d7..21d13439ad 100644
--- a/bootstraptest/test_block.rb
+++ b/bootstraptest/test_block.rb
@@ -335,3 +335,11 @@ assert_equal %q{[1, nil]}, %q{
     [i, j]
   }
 }
+
+# [ruby-dev:31147]
+assert_equal 'nil', %q{
+  def m
+    yield
+  end
+  m{|&b| b}.inspect
+}
diff --git a/insnhelper.ci b/insnhelper.ci
index f3665be14f..385a31eda9 100644
--- a/insnhelper.ci
+++ b/insnhelper.ci
@@ -605,7 +605,7 @@ vm_yield_with_cfunc(rb_thread_t *th, rb_block_t *block,
 
 static inline int
 vm_yield_setup_args(rb_thread_t *th, rb_iseq_t *iseq,
-		    int argc, VALUE *argv, int lambda)
+		    int argc, VALUE *argv, rb_block_t *blockptr, int lambda)
 {
     if (0) { /* for debug */
 	printf("     argc: %d\n", argc);
@@ -620,20 +620,8 @@ vm_yield_setup_args(rb_thread_t *th, rb_iseq_t *iseq,
 
     if (lambda) {
 	/* call as method */
-	if (iseq->arg_block != -1) {
-	    volatile VALUE procval = Qnil;
-
-	    if (rb_block_given_p()) {
-		rb_block_t *blockptr;
-		rb_proc_t *proc;
-		procval = rb_block_proc();
-		GetProcPtr(procval, proc);
-		blockptr = &proc->block;
 		return vm_callee_setup_arg(th, iseq, argc, argv, &blockptr);
 	    }
-	}
-	return vm_callee_setup_arg(th, iseq, argc, argv, 0);
-    }
     else {
 	int i;
 	const int m = iseq->argc;
@@ -721,13 +709,13 @@ vm_yield_setup_args(rb_thread_t *th, rb_iseq_t *iseq,
 
 	/* {|&b|} */
 	if (iseq->arg_block != -1) {
-	    VALUE proc = Qnil;
+	    VALUE procval = Qnil;
 
-	    if (rb_block_given_p()) {
-		proc = rb_block_proc();
+	    if (blockptr) {
+		procval = blockptr->proc;
 	    }
 
-	    argv[iseq->arg_block] = proc;
+	    argv[iseq->arg_block] = procval;
 	    th->mark_stack_len = iseq->arg_block + 1;
 	}
 
diff --git a/insns.def b/insns.def
index 59c924f166..e1b28766cb 100644
--- a/insns.def
+++ b/insns.def
@@ -1268,7 +1268,7 @@ invokeblock
 	CHECK_STACK_OVERFLOW(GET_CFP(), iseq->stack_max);
 
 	DEC_SP(argc);
-	opt_pc = vm_yield_setup_args(th, iseq, argc, GET_SP(),
+	opt_pc = vm_yield_setup_args(th, iseq, argc, GET_SP(), 0,
 				     block_proc_is_lambda(block->proc));
 	argc = iseq->arg_size;
 	INC_SP(argc);
diff --git a/version.h b/version.h
index f1538f4d4e..dac25e2441 100644
--- a/version.h
+++ b/version.h
@@ -1,7 +1,7 @@
 #define RUBY_VERSION "1.9.0"
-#define RUBY_RELEASE_DATE "2007-07-06"
+#define RUBY_RELEASE_DATE "2007-07-07"
 #define RUBY_VERSION_CODE 190
-#define RUBY_RELEASE_CODE 20070706
+#define RUBY_RELEASE_CODE 20070707
 #define RUBY_PATCHLEVEL 0
 
 #define RUBY_VERSION_MAJOR 1
@@ -9,7 +9,7 @@
 #define RUBY_VERSION_TEENY 0
 #define RUBY_RELEASE_YEAR 2007
 #define RUBY_RELEASE_MONTH 7
-#define RUBY_RELEASE_DAY 6
+#define RUBY_RELEASE_DAY 7
 
 #ifdef RUBY_EXTERN
 RUBY_EXTERN const char ruby_version[];
diff --git a/vm.c b/vm.c
index 736494fe86..e8507743fe 100644
--- a/vm.c
+++ b/vm.c
@@ -559,7 +559,22 @@ invoke_block(rb_thread_t *th, rb_block_t *block, VALUE self, int argc, VALUE *ar
 	    th->cfp->sp[i] = argv[i];
 	}
 
-	opt_pc = vm_yield_setup_args(th, iseq, argc, th->cfp->sp, type == FRAME_MAGIC_LAMBDA);
+	if (iseq->arg_block == -1) {
+	    opt_pc = vm_yield_setup_args(th, iseq, argc, th->cfp->sp, 0,
+					 type == FRAME_MAGIC_LAMBDA);
+	}
+	else {
+	    rb_block_t *blockptr = 0;
+	    if (rb_block_given_p()) {
+		rb_proc_t *proc;
+		VALUE procval;
+		procval = rb_block_proc();
+		GetProcPtr(procval, proc);
+		blockptr = &proc->block;
+	    }
+	    opt_pc = vm_yield_setup_args(th, iseq, argc, th->cfp->sp,
+					 blockptr, type == FRAME_MAGIC_LAMBDA);
+	}
 	argc = iseq->arg_size;
 	th->cfp->sp += argc;