Index: trunk/psphot/src/psphotApResid.c
===================================================================
--- trunk/psphot/src/psphotApResid.c	(revision 15078)
+++ trunk/psphot/src/psphotApResid.c	(revision 15143)
@@ -270,5 +270,8 @@
 
     *errorScale = stats->sampleMedian;
-    *errorFloor = dSo->data.F32[0];
+    for (int i = 0; i < dSo->n; i++) {
+	*errorFloor = dSo->data.F32[i];
+	if (isfinite(*errorFloor)) break;
+    }
 
     psFree (stats);