diff --git a/python/lsst/ip/diffim/subtractImages.py b/python/lsst/ip/diffim/subtractImages.py
index cffced91..b4174181 100644
--- a/python/lsst/ip/diffim/subtractImages.py
+++ b/python/lsst/ip/diffim/subtractImages.py
@@ -558,23 +558,30 @@ def finalize(self, template, science, difference, kernel,
         """
         # Erase existing detection mask planes.
         #  We don't want the detection mask from the science image
+        bbox = science.getBBox()
         mask = difference.mask
         mask &= ~(mask.getPlaneBitMask("DETECTED") | mask.getPlaneBitMask("DETECTED_NEGATIVE"))
 
         # propagate the mask plane related to Fake source injection
         # NOTE: the fake source injection sets FAKE plane, but it should be INJECTED
-        diffInjectedBitMask = mask.addMaskPlane("INJECTED")
-        diffInjectedTemplateBitMask = mask.addMaskPlane("INJECTED_TEMPLATE")
+        self.log.info("Adding injected mask planes")
+        diffInjectedMaskPlane = mask.addMaskPlane("INJECTED")
+        diffInjectedTemplateMaskPlane = mask.addMaskPlane("INJECTED_TEMPLATE")
+
+        scienceFakeMaskPlane = science.mask.getMaskPlane('FAKE')
+        scienceFakeBitMask = science.mask.getPlaneBitMask('FAKE')
+        templateFakeMaskPlane = template.mask.getMaskPlane('FAKE')
+        templateFakeBitMask = template[bbox].mask.getPlaneBitMask('FAKE')
 
-        scienceFakeBit = science.mask.getPlaneBitMask('FAKE')
-        templateFakeBit = template.mask.getPlaneBitMask('FAKE')
+        # self.log.info(f"Adding {np.sum(scienceFakeBitMask> 0)} pixels from science to Injected mask")
+        #  self.log.info(f"and {np.sum(templateFakeBitMask>0)} pixels from templated to Injected mask")
 
-        deltaBitScience = diffInjectedBitMask - scienceFakeBit
-        deltaBitTemplate = diffInjectedTemplateBitMask - templateFakeBit
+        deltaMaskPlaneScience = 2**(diffInjectedMaskPlane - scienceFakeMaskPlane)
+        deltaMaskPlaneTemplate = 2**(diffInjectedTemplateMaskPlane - templateFakeMaskPlane)
 
         # get the arrays from the template and science that are flagged as FAKE
-        injectedScienceMaskArray = (science.mask.array & scienceFakeBit) * (2**deltaBitScience)
-        injectedTemplateMaskArray = (template.mask.array & templateFakeBit) * (2**deltaBitTemplate)
+        injectedScienceMaskArray = (science.mask.array & scienceFakeBitMask) * deltaMaskPlaneScience
+        injectedTemplateMaskArray = (template[bbox].mask.array & templateFakeBitMask) * deltaMaskPlaneTemplate
 
         mask.array |= injectedScienceMaskArray
         mask.array |= injectedTemplateMaskArray