diff --git a/pycbc/scheme.py b/pycbc/scheme.py
index <HASH>..<HASH> 100644
--- a/pycbc/scheme.py
+++ b/pycbc/scheme.py
@@ -111,7 +111,6 @@ class CUDAScheme(DefaultScheme):
 
 class OpenCLScheme(DefaultScheme):
     """Context that sets PyCBC objects to use a OpenCL processing scheme. """
-    _single = None
     def __init__(self,platform_name=None,device_num=0):
         DefaultScheme.__init__(self)
         if not pycbc.HAVE_OPENCL:
removed unused _single=None in scheme.py