diff --git a/galsim/des/des_psfex.py b/galsim/des/des_psfex.py
index e994fe40ed0..5291786e9bd 100644
--- a/galsim/des/des_psfex.py
+++ b/galsim/des/des_psfex.py
@@ -36,7 +36,7 @@ class DES_PSFEx(object):
         
         ...
 
-        pos = galsim.Position(image_x, image_y)  # position in pixels on the image
+        pos = galsim.PositionD(image_x, image_y)  # position in pixels on the image
                                                  # NOT in arcsec on the sky!
         psf = des_psfex.getPSF(pos, pixel_scale=0.27)