diff --git a/src/mac/carbon/clipbrd.cpp b/src/mac/carbon/clipbrd.cpp
index cda81e29bb..4267942472 100644
--- a/src/mac/carbon/clipbrd.cpp
+++ b/src/mac/carbon/clipbrd.cpp
@@ -251,10 +251,12 @@ bool wxClipboard::AddData( wxDataObject *data )
                case wxDF_TEXT:
                case wxDF_OEMTEXT:
                     mactype = kScrapFlavorTypeText ;
+                    sz -= 1;
                break ;
     #if wxUSE_UNICODE
                case wxDF_UNICODETEXT :
                     mactype = kScrapFlavorTypeUnicode ;
+                    sz -= 2;
                break ;
     #endif
     #if wxUSE_DRAG_AND_DROP