diff --git a/src/include/isam.cpp b/src/include/isam.cpp
index 270163727..2d3098d5b 100755
--- a/src/include/isam.cpp
+++ b/src/include/isam.cpp
@@ -3220,7 +3220,11 @@ void TRectype::unknown_field(const char* name) const
   static int last_file = 0;
   if (_logicnum != last_file)
   {
-    NFCHECK("Il campo '%s' non appartiene al file %d", name, _logicnum);
+#ifdef DBG
+		NFCHECK("Il campo '%s' non appartiene al file %d", name, _logicnum);
+#else
+		fatal_box("Database non convertito.\nIl campo '%s' non appartiene al file %d", name, _logicnum);
+#endif
     last_file = _logicnum;
   }
 }