diff --git a/src/Registration/cReg/NiftiImageData.cpp b/src/Registration/cReg/NiftiImageData.cpp
index 6afbbe56c..9f9e25d30 100644
--- a/src/Registration/cReg/NiftiImageData.cpp
+++ b/src/Registration/cReg/NiftiImageData.cpp
@@ -220,7 +220,7 @@ void NiftiImageData<dataType>::construct_NiftiImageData_from_complex_im_real_com
 
     auto &it_in = in_sptr->begin();
     auto &it_out = out_sptr->begin();
-    for (; it_in!=in_sptr->end(); ++it_in, ++it_out)
+    for (; it_out != out_sptr->end(); ++it_in, ++it_out)
         *it_out = (*it_in).complex_float().real();
 }
 
@@ -235,7 +235,7 @@ void NiftiImageData<dataType>::construct_NiftiImageData_from_complex_im_imag_com
 
     auto &it_in = in_sptr->begin();
     auto &it_out = out_sptr->begin();
-    for (; it_in!=in_sptr->end(); ++it_in, ++it_out)
+    for (; it_out != out_sptr->end(); ++it_in, ++it_out)
         *it_out = (*it_in).complex_float().imag();
 }
 
diff --git a/src/Registration/pReg/Reg.py b/src/Registration/pReg/Reg.py
index d05103eb9..9f588663a 100644
--- a/src/Registration/pReg/Reg.py
+++ b/src/Registration/pReg/Reg.py
@@ -1108,10 +1108,26 @@ def set_padding_value(self, val):
     def norm(self, num_iter=2, verb=0):
         '''Computes the norm of the forward projection operator.
         '''
+        # reference and floating images need to be real.
+        if self.reference_image.is_complex():
+            reference_image, _ = NiftiImageData.construct_from_complex_image(self.reference_image)
+            parms.set_parameter(
+                self.handle, self.name, 'reference_image', reference_image.handle)
+        if self.floating_image.is_complex():
+            floating_image, _ = NiftiImageData.construct_from_complex_image(self.floating_image)
+            parms.set_parameter(
+                self.handle, self.name, 'floating_image', floating_image.handle)
         handle = pyreg.cReg_NiftyResampler_norm(self.handle, num_iter, verb)
         check_status(handle)
         r = pyiutil.floatDataFromHandle(handle)
         pyiutil.deleteDataHandle(handle)
+        # Restore reference and floating images.
+        if self.reference_image.is_complex():
+            parms.set_parameter(
+                self.handle, self.name, 'reference_image', self.reference_image.handle)
+        if self.floating_image.is_complex():
+            parms.set_parameter(
+                self.handle, self.name, 'floating_image', self.floating_image.handle)
         return r;
 
     def process(self):