Index: /trunk/psphot/src/pmFootprint.c
===================================================================
--- /trunk/psphot/src/pmFootprint.c	(revision 13348)
+++ /trunk/psphot/src/pmFootprint.c	(revision 13349)
@@ -1033,5 +1033,5 @@
 	const float stdev = sqrt(subWt->data.F32[y][x]);
 	float threshold = subImg->data.F32[y][x] - nsigma_delta*stdev;
-	if (threshold < min_threshold) {
+	if (isnan(threshold) || threshold < min_threshold) {
 #if 1					// min_threshold is assumed to be below the detection threshold,
 					// so all the peaks are pmFootprint, and this isn't the brightest