diff --git a/include/wx/sizer.h b/include/wx/sizer.h
index aa14476d05..f4b0b4ba8a 100644
--- a/include/wx/sizer.h
+++ b/include/wx/sizer.h
@@ -827,7 +827,7 @@ class WXDLLIMPEXP_CORE wxFlexGridSizer: public wxGridSizer
 public:
     // ctors specifying the number of columns only: number of rows will be
     // deduced automatically depending on the number of sizer elements
-    wxFlexGridSizer( int cols, int vgap, int hgap = 0);
+    wxFlexGridSizer( int cols, int vgap, int hgap );
     wxFlexGridSizer( int cols, const wxSize& gap = wxSize(0, 0) );
 
     // ctors specifying the number of rows and columns
diff --git a/interface/wx/sizer.h b/interface/wx/sizer.h
index 6e6d1f36a4..cfd1dd841c 100644
--- a/interface/wx/sizer.h
+++ b/interface/wx/sizer.h
@@ -1446,7 +1446,7 @@ public:
 
         @since 2.9.1 (except for the four argument overload)
     */
-    wxFlexGridSizer( int cols, int vgap, int hgap = 0 );
+    wxFlexGridSizer( int cols, int vgap, int hgap );
     wxFlexGridSizer( int cols, const wxSize& gap = wxSize(0, 0) );
 
     wxFlexGridSizer( int rows, int cols, int vgap, int hgap );