diff --git a/ChangeLog b/ChangeLog
index 4d69391762..aeb9b9463d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Wed Jun 29 08:45:53 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* proc.c (passed_block): convert passed block symbol to proc.
+	  based on the patch by Daisuke Sato in [ruby-dev:49695].
+	  [Bug #12531]
+
 Wed Jun 29 03:34:41 2016  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* bignum.c (rb_big2ulong): the old logic seems to try to avoid
diff --git a/proc.c b/proc.c
index 850de22634..29a857f4a4 100644
--- a/proc.c
+++ b/proc.c
@@ -820,6 +820,9 @@ passed_block(VALUE pass_procval)
 {
     if (!NIL_P(pass_procval)) {
 	rb_proc_t *pass_proc;
+	if (SYMBOL_P(pass_procval)) {
+	    pass_procval = sym_proc_new(rb_cProc, pass_procval);
+	}
 	GetProcPtr(pass_procval, pass_proc);
 	return &pass_proc->block;
     }
diff --git a/test/ruby/test_symbol.rb b/test/ruby/test_symbol.rb
index 03934226a1..d8c91c1eea 100644
--- a/test/ruby/test_symbol.rb
+++ b/test/ruby/test_symbol.rb
@@ -229,6 +229,35 @@ class TestSymbol < Test::Unit::TestCase
     assert_equal([false, false], m2.call(self, m2), "#{bug8531} nested without block")
   end
 
+  def test_block_curry_proc
+    assert_separately([], "#{<<-"begin;"}\n#{<<-"end;"}")
+    begin;
+    b = proc { true }.curry
+    assert(b.call, "without block")
+    assert(b.call { |o| o.to_s }, "with block")
+    assert(b.call(&:to_s), "with sym block")
+    end;
+  end
+
+  def test_block_curry_lambda
+    assert_separately([], "#{<<-"begin;"}\n#{<<-"end;"}")
+    begin;
+    b = lambda { true }.curry
+    assert(b.call, "without block")
+    assert(b.call { |o| o.to_s }, "with block")
+    assert(b.call(&:to_s), "with sym block")
+    end;
+  end
+
+  def test_block_method_to_proc
+    assert_separately([], "#{<<-"begin;"}\n#{<<-"end;"}")
+    begin;
+    b = method(:tap).to_proc
+    assert(b.call { |o| o.to_s }, "with block")
+    assert(b.call(&:to_s), "with sym block")
+    end;
+  end
+
   def test_succ
     assert_equal(:fop, :foo.succ)
   end