diff --git a/hexrd/instrument/detector.py b/hexrd/instrument/detector.py
index 7b58c0e30..1b9afa345 100644
--- a/hexrd/instrument/detector.py
+++ b/hexrd/instrument/detector.py
@@ -637,10 +637,13 @@ def config_dict(self, chi=0, tvec=ct.zeros_3,
                 columns=int(self.cols),
                 size=[float(self.pixel_size_row),
                       float(self.pixel_size_col)],
-                roi=roi
             )
         )
 
+        if roi is not None:
+            # Only add roi if it is not None
+            det_dict['pixels']['roi'] = roi
+
         # distortion
         if self.distortion is not None:
             dparams = self.distortion.params