diff --git a/spec/ruby/core/kernel/backtick_spec.rb b/spec/ruby/core/kernel/backtick_spec.rb
index 045bb598cd..834d5636c1 100644
--- a/spec/ruby/core/kernel/backtick_spec.rb
+++ b/spec/ruby/core/kernel/backtick_spec.rb
@@ -37,7 +37,7 @@ describe "Kernel#`" do
 
   platform_is_not :windows do
     it "handles invalid UTF-8 bytes in command" do
-      `echo "testing\xC2 a non UTF-8 string"`.should == "testing\xC2 a non UTF-8 string\n"
+      `echo "testing\xC2 a non UTF-8 string"`.b.should == "testing\xC2 a non UTF-8 string\n".b
     end
 
     it "sets $? to the exit status of the executed sub-process" do