diff --git a/pyFAI/opencl/common.py b/pyFAI/opencl/common.py
index c0671580e..9751142d6 100644
--- a/pyFAI/opencl/common.py
+++ b/pyFAI/opencl/common.py
@@ -34,21 +34,19 @@
 __contact__ = "Jerome.Kieffer@ESRF.eu"
 __license__ = "MIT"
 __copyright__ = "2012-2017 European Synchrotron Radiation Facility, Grenoble, France"
-__date__ = "11/09/2017"
+__date__ = "14/09/2017"
 __status__ = "stable"
 __all__ = ["ocl", "pyopencl", "mf", "release_cl_buffers", "allocate_cl_buffers",
            "measure_workgroup_size", "kernel_workgroup_size"]
 
 import os
 import logging
-import gc
-
 import numpy
 
 
 logger = logging.getLogger("pyFAI.opencl.common")
 
-from .utils import get_opencl_code, concatenate_cl_kernel
+from .utils import get_opencl_code
 
 if os.environ.get("PYFAI_OPENCL") in ["0", "False"]:
     logger.warning("Use of OpenCL has been disables from environment variable: SILX_OPENCL=0")
@@ -59,13 +57,15 @@
     except ImportError:
         logger.warning("Unable to import pyOpenCl. Please install it from: http://pypi.python.org/pypi/pyopencl")
         pyopencl = None
-        class mf(object):
-            WRITE_ONLY = 1
-            READ_ONLY = 1
-            READ_WRITE = 1
     else:
         import pyopencl.array as array
         mf = pyopencl.mem_flags
+if pyopencl is None:
+    # create a dummy object
+    class mf(object):
+        WRITE_ONLY = 1
+        READ_ONLY = 1
+        READ_WRITE = 1
 
 FLOP_PER_CORE = {"GPU": 64,  # GPU, Fermi at least perform 64 flops per cycle/multicore, G80 were at 24 or 48 ...
                  "CPU": 4,  # CPU, at least intel's have 4 operation per cycle