Index: trunk/psModules/src/objects/pmSourcePhotometry.c
===================================================================
--- trunk/psModules/src/objects/pmSourcePhotometry.c	(revision 34403)
+++ trunk/psModules/src/objects/pmSourcePhotometry.c	(revision 34498)
@@ -165,4 +165,6 @@
             status = pmSourcePhotometryModel (&model->mag, NULL, model);
             if (model == source->modelEXT) foundEXT = true;
+	    float SN = fabs(model->params->data.F32[PM_PAR_I0] / model->dparams->data.F32[PM_PAR_I0]);
+	    model->magErr = 1.0 / SN;
         }
         if (foundEXT) {