diff --git a/spec/ruby/core/io/popen_spec.rb b/spec/ruby/core/io/popen_spec.rb
index 45bb0e2cab..2d60c4c0f7 100644
--- a/spec/ruby/core/io/popen_spec.rb
+++ b/spec/ruby/core/io/popen_spec.rb
@@ -23,6 +23,7 @@ describe "IO.popen" do
   it "raises IOError when writing a read-only pipe" do
     @io = IO.popen(ruby_cmd('puts "foo"'), "r")
     lambda { @io.write('foo') }.should raise_error(IOError)
+    @io.read.should == "foo\n"
   end
 end