diff --git a/ObservationSim/ObservationSim.py b/ObservationSim/ObservationSim.py
index 3d31a0d1e66179ef3513997bc9d3788d7f7fe7b6..33321bb65dce7ef89ab966d3319ce07ad1fd6c9e 100755
--- a/ObservationSim/ObservationSim.py
+++ b/ObservationSim/ObservationSim.py
@@ -295,6 +295,8 @@ class Observation(object):
                     # chip_output.logger.info("current filter type: %s"%filt.filter_type)
                     if self.config["run_option"]["out_cat_only"]:
                         isUpdated = True
+                        obj.real_pos = obj.getRealPos(chip.img, global_x=obj.posImg.x, global_y=obj.posImg.y,
+                                        img_real_wcs=obj.real_wcs)
                         pos_shear = 0.
                     elif chip.survey_type == "photometric" and not self.config["run_option"]["out_cat_only"]:
                         isUpdated, pos_shear = obj.drawObj_multiband(