Index: trunk/psModules/src/objects/models/pmModel_QGAUSS.c
===================================================================
--- trunk/psModules/src/objects/models/pmModel_QGAUSS.c	(revision 33409)
+++ trunk/psModules/src/objects/models/pmModel_QGAUSS.c	(revision 33417)
@@ -402,4 +402,9 @@
     assert (psf->params->n > PM_PAR_YPOS);
     assert (psf->params->n > PM_PAR_XPOS);
+
+    if (! isfinite(Io)) {
+        fprintf(stderr, "non-finite Io passed to PM_MODEL_PARAMS_FROM_PSF\n");
+        return false;
+    }
 
     PAR[PM_PAR_SKY]  = 0.0;