diff -u ml4.i.orig ml4.i
--- ml4.i.orig
+++ ml4.i
@@ -124,7 +124,10 @@ func ml4write(file,data,varname,mode,endian=)
     ncols=int(dims(3));
   }
   
-  if      (structof(data)==long)   { type='l'; }
+  tmp = data; // otherwise data may be swapped in place in endian='L'
+
+  // next line: fix from Thibaut Paumard for Debian.
+  if      (structof(data)==long)   { type='l'; tmp=int(tmp); }
   else if (structof(data)==int)    { type='l'; }
   else if (structof(data)==float)  { type='r'; }
   else if (structof(data)==double) { type='d'; }
@@ -132,8 +135,6 @@ func ml4write(file,data,varname,mode,endian=)
   else if (structof(data)==char)   { type='b'; }
   else error,"Unsupported type";
 
-  tmp = data; // otherwise data may be swapped in place in endian='L'
-  
   status = matout(file,varname,&tmp,nrows,ncols,type,mode,endian);
   if (status) error,"write failed";
 }