Index: trunk/Mars/mcore/fits.h
===================================================================
--- trunk/Mars/mcore/fits.h	(revision 19394)
+++ trunk/Mars/mcore/fits.h	(revision 19404)
@@ -287,5 +287,5 @@
 
             const std::string tFormName = is_compressed ? "ZFORM" : "TFORM";
-            for (long long unsigned int i=1; i<=num_cols; i++)
+            for (size_t i=1; i<=num_cols; i++)
             {
                 const std::string num(std::to_string(i));