Index: trunk/Mars/mfileio/MWriteFitsFile.cc
===================================================================
--- trunk/Mars/mfileio/MWriteFitsFile.cc	(revision 18569)
+++ trunk/Mars/mfileio/MWriteFitsFile.cc	(revision 18570)
@@ -525,9 +525,5 @@
             return kFALSE;
 
-         char attrName[10];
-         sprintf(attrName, "CLNAME%d", num);
-         num++;
-
-         InitAttr(attrName,
+         InitAttr(Form("CLNAME%d", num),
                   "A",
                   (void*)i_subTable->first.Data(),
@@ -536,4 +532,12 @@
                   fitsTable);
 
+         InitAttr(Form("CLTYPE%d", num),
+                  "A",
+                  (void*)i_subTable->second.GetContainer()->ClassName(),
+                  NULL,
+                  "MARS container class",
+                  fitsTable);
+
+         num++;
          i_subTable++;
          }