diff --git a/scripts/csresmap.py b/scripts/csresmap.py
index 848cfbb..b4bb983 100755
--- a/scripts/csresmap.py
+++ b/scripts/csresmap.py
@@ -291,21 +291,21 @@ class csresmap(gammalib.GApplication):
             
             # Subtract and divide by model map
             self.resmap -= modelmap
-            #self.resmap /= modelmap   # Python 3.x does not like this !!!
-            for pixel in modelmap:
-                if pixel != 0.0:
-                    pixel = 1.0/pixel
-            self.resmap *= modelmap
+            self.resmap /= modelmap   # Python 3.x does not like this !!!
+            #for pixel in modelmap:
+            #    if pixel != 0.0:
+            #        pixel = 1.0/pixel
+            #self.resmap *= modelmap
             
         elif self.m_algorithm == "SUBDIVSQRT":
 
             # subtract and divide by sqrt of model map
             self.resmap -= modelmap
-            #self.resmap /= modelmap.sqrt()   # Python 3.x does not like this !!!
-            for pixel in modelmap:
-                if pixel != 0.0:
-                    pixel = 1.0/math.sqrt(pixel)
-            self.resmap *= modelmap
+            self.resmap /= modelmap.sqrt()   # Python 3.x does not like this !!!
+            #for pixel in modelmap:
+            #    if pixel != 0.0:
+            #        pixel = 1.0/math.sqrt(pixel)
+            #self.resmap *= modelmap
             
         else: