diff --git a/test/dtrace/helper.rb b/test/dtrace/helper.rb
index 2243d15c95..7683a6a887 100644
--- a/test/dtrace/helper.rb
+++ b/test/dtrace/helper.rb
@@ -30,7 +30,6 @@ if ok
     begin
       require 'pty'
     rescue LoadError
-      ok = false
     end
   end
 end
@@ -78,7 +77,7 @@ module DTrace
           Process.wait(pid)
         end
         lines
-      end
+      end if defined?(PTY)
     end
 
     # only handles simple cases, use a Hash for d_program