diff --git a/include/msksheet.h b/include/msksheet.h
index 34f3e4917..e64106645 100755
--- a/include/msksheet.h
+++ b/include/msksheet.h
@@ -131,7 +131,7 @@ public:
   TString_array& rows_array() const;
   // @cmember Ritorna l'elemento <p c>-esimo della riga <p r>
   const char* cell(int r, int c)
-  { return row(r).get(c); }
+  { const char*v=row(r).get(c);  return v ? v: " "; }
 
   // @cmember Ritorna la prima riga vuota nello spreadsheet
   int first_empty() const;