diff --git a/parse.y b/parse.y
index 3eee213aab..3fa862d56b 100644
--- a/parse.y
+++ b/parse.y
@@ -1298,7 +1298,12 @@ command_asgn	: lhs '=' command_rhs
 
 			value_expr($6);
 			$3 = make_array($3, &@3);
-			args = arg_concat(p, $3, $6, &@$);
+			if (nd_type($3) == NODE_BLOCK_PASS) {
+			    args = NEW_ARGSCAT($3, $6, &@$);
+			}
+			else {
+			    args = arg_concat(p, $3, $6, &@$);
+			}
 			$$ = NEW_OP_ASGN1($1, $5, args, &@$);
 			fixpos($$, $1);
 		    /*%
diff --git a/test/ruby/test_parse.rb b/test/ruby/test_parse.rb
index 41aad0050d..e843c66242 100644
--- a/test/ruby/test_parse.rb
+++ b/test/ruby/test_parse.rb
@@ -457,6 +457,30 @@ class TestParse < Test::Unit::TestCase
     end
   end
 
+  def test_op_asgn1_with_block
+    t = Object.new
+    a = []
+    blk = proc {|x| a << x }
+    def t.[](_)
+      yield(:aref)
+      nil
+    end
+    def t.[]=(_, _)
+      yield(:aset)
+    end
+    def t.dummy(_)
+    end
+    eval <<-END, nil, __FILE__, __LINE__+1
+      t[42, &blk] ||= 42
+    END
+    assert_equal([:aref, :aset], a)
+    a.clear
+    eval <<-END, nil, __FILE__, __LINE__+1
+    t[42, &blk] ||= t.dummy 42 # command_asgn test
+    END
+    assert_equal([:aref, :aset], a)
+  end
+
   def test_backquote
     t = Object.new