# http://www.astromatic.net/forum/showthread.php?tid=1041
# https://gist.githubusercontent.com/mwcraig/48da565e91669bf1b93a/raw/5e4ad72f6626e7866b733546f89d00b0dfe70434/field.c.diff
--- src/field.c	2015-11-15 11:43:20.000000000 -0500
+++ src/field.c	2015-11-15 11:43:51.000000000 -0500
@@ -340,7 +340,7 @@
       nsample += set[n]->nsample;
       free_tab(set[n]->imatab);
       set[n]->imatab = NULL;
-      set[n]->setindex = n++;
+      set[n]->setindex = n; n++;
       }
 
   field->nsample = nsample;