diff --git a/python/desc/imsim/flats.py b/python/desc/imsim/flats.py
index d3b3e82e..c6b6e191 100644
--- a/python/desc/imsim/flats.py
+++ b/python/desc/imsim/flats.py
@@ -41,6 +41,8 @@ def make_flat(gs_det, counts_per_iter, niter, rng, buf=2, logger=None,
     -------
     galsim.ImageF
     """
+    config = desc.imsim.read_config()
+
     if logger is None:
         logger = desc.imsim.get_logger('DEBUG', name='make_flat')
     if wcs is None:
@@ -49,6 +51,7 @@ def make_flat(gs_det, counts_per_iter, niter, rng, buf=2, logger=None,
     nrow = gs_det.yMaxPix - gs_det.yMinPix + 1
     flat = galsim.ImageF(ncol, nrow, wcs=wcs)
     sensor = galsim.SiliconSensor(rng=rng,
+                                  strength=config['ccd']['bf_strength'],
                                   treering_center=gs_det.tree_rings.center,
                                   treering_func=gs_det.tree_rings.func,
                                   transpose=True)
diff --git a/python/desc/imsim/skyModel.py b/python/desc/imsim/skyModel.py
index 69a7f1ff..61bbe508 100755
--- a/python/desc/imsim/skyModel.py
+++ b/python/desc/imsim/skyModel.py
@@ -283,9 +283,11 @@ def addNoiseAndBackground(self, image, bandpass=None, m5=None,
         # Use the transpose=True option since "eimages" of LSST sensors
         # follow the Camera Coordinate System convention where the
         # parallel transfer direction is along the x-axis.
-        nrecalc = 1e300 # disable pixel boundary updating.
+        config = get_config()
+        nrecalc = 1e300  # disable pixel boundary updating.
         sensor = galsim.SiliconSensor(rng=self.randomNumbers,
                                       nrecalc=nrecalc,
+                                      strength=config['ccd']['bf_strength'],
                                       treering_func=detector.tree_rings.func,
                                       treering_center=detector.tree_rings.center,
                                       transpose=True)
@@ -462,11 +464,14 @@ def process_photons(self, image, skyCounts, detector, chunk_size=int(5e6)):
         nrow, ncol = image.array.shape
         dx = ncol//nx   # number of pixels in x for an amp
         dy = nrow//ny   # number of pixels in y
+
+        config = get_config()
         # Disable the updating of the pixel boundaries by
         # setting nrecalc to 1e300
         nrecalc = 1e300
         sensor = galsim.SiliconSensor(rng=self.randomNumbers,
                                       nrecalc=nrecalc,
+                                      strength=config['ccd']['bf_strength'],
                                       treering_center=tree_rings.center,
                                       treering_func=tree_rings.func,
                                       transpose=True)