diff --git a/include/maskfld.cpp b/include/maskfld.cpp
index 545911c56..5329c1795 100755
--- a/include/maskfld.cpp
+++ b/include/maskfld.cpp
@@ -90,6 +90,8 @@ char TMask_field::TField_Flags::update(const char* f)
       ghost = TRUE; break;
     case 'H': 
       show_default  = shown = FALSE; break;
+    case 'I': 
+      break; // reserved for sheetfield insert
     case 'M': 
       roman = TRUE; break;
     case 'P':