diff --git a/test/ruby/test_iseq.rb b/test/ruby/test_iseq.rb
index ede333fd14..4af440ae42 100644
--- a/test/ruby/test_iseq.rb
+++ b/test/ruby/test_iseq.rb
@@ -125,7 +125,7 @@ class TestISeq < Test::Unit::TestCase
     assert_same a, b
   end
 
-  def test_diable_opt
+  def test_disable_opt
     src = "a['foo'] = a['bar']; 'a'.freeze"
     _,_,_,_,_,_,_,_,_,_,_,_,_,body= RubyVM::InstructionSequence.compile(src, __FILE__, __FILE__, __LINE__, false).to_a
     body.each{|insn|