Index: /trunk/Mars/mfileio/MWriteFitsFile.cc
===================================================================
--- /trunk/Mars/mfileio/MWriteFitsFile.cc	(revision 19433)
+++ /trunk/Mars/mfileio/MWriteFitsFile.cc	(revision 19434)
@@ -1221,7 +1221,9 @@
    fClHelper.clear();
 
+   const Bool_t hasrule = fRule.BeginsWith("s/") && fRule.EndsWith("/");
+
    // get new filename
    const TString readFileName = read->GetFullFileName();
-   const TString newname = MWriteRootFile::SubstituteName(fRule, readFileName);
+   const TString newname = hasrule ? MWriteRootFile::SubstituteName(fRule, readFileName) : fRule;
 
    // create new files