diff --git a/tp/tp0900.cpp b/tp/tp0900.cpp
index 33e4fa939..368d70a80 100755
--- a/tp/tp0900.cpp
+++ b/tp/tp0900.cpp
@@ -660,7 +660,7 @@ void TDichiarazione_CONAI::elabora(const TMask& mask) const
     TFilename path = mask.get(F_PATH); 
 		path.lower();
 		if (path.ends_with("xls") || path.ends_with("slk"))
-      csv->save_as(path, fmt_unknown);
+      csv->save_as(path, fmt_html);
 		else
 			csv->save_as(path);