diff --git a/include/wx/notebook.h b/include/wx/notebook.h
index 2d5de60566..61c2d2e6b8 100644
--- a/include/wx/notebook.h
+++ b/include/wx/notebook.h
@@ -48,7 +48,6 @@ enum
 #define wxNB_FIXEDWIDTH       0x0100
 #define wxNB_MULTILINE        0x0200
 #define wxNB_NOPAGETHEME      0x0400
-#define wxNB_FLAT             0x0800
 
 
 typedef wxWindow wxNotebookPage;  // so far, any window can be a page
diff --git a/src/common/nbkbase.cpp b/src/common/nbkbase.cpp
index 42de7672f3..b8d3eb54f4 100644
--- a/src/common/nbkbase.cpp
+++ b/src/common/nbkbase.cpp
@@ -80,7 +80,6 @@ wxFLAGS_MEMBER(wxBK_LEFT)
 wxFLAGS_MEMBER(wxBK_RIGHT)
 wxFLAGS_MEMBER(wxBK_BOTTOM)
 wxFLAGS_MEMBER(wxNB_NOPAGETHEME)
-wxFLAGS_MEMBER(wxNB_FLAT)
 wxEND_FLAGS( wxNotebookStyle )
 
 #if wxUSE_EXTENDED_RTTI