Index: /trunk/psphot/src/psphotMakeResiduals.c
===================================================================
--- /trunk/psphot/src/psphotMakeResiduals.c	(revision 18037)
+++ /trunk/psphot/src/psphotMakeResiduals.c	(revision 18038)
@@ -168,4 +168,7 @@
                 dfluxes->data.F32[i] = dflux;
                 fmasks->data.U8[i] = mflux;
+		if (isnan(flux)) { 
+		    fmasks->data.U8[i] = 1;
+		}
                 // fprintf (stderr, "%f %f : %f %f (%d)\n", ix, iy, flux, dflux, fmasks->data.U8[i]);
             }