diff --git a/include/wx/cocoa/combobox.h b/include/wx/cocoa/combobox.h
index 3ac38165e4..2b665585d3 100644
--- a/include/wx/cocoa/combobox.h
+++ b/include/wx/cocoa/combobox.h
@@ -63,7 +63,8 @@ public:
     virtual void SetSelection(int);
     // Overlapping methods
     virtual wxString GetStringSelection();
-    virtual void SetStringSelection(wxString& selection);
+    // other methods
+    virtual void SetStringSelection(const wxString& selection);
     // wxItemContainer
     virtual void Clear();
     virtual void Delete(int);
diff --git a/src/cocoa/combobox.mm b/src/cocoa/combobox.mm
index 4101d8f3d5..eb3f4b104f 100644
--- a/src/cocoa/combobox.mm
+++ b/src/cocoa/combobox.mm
@@ -63,7 +63,7 @@ wxString wxComboBox::GetStringSelection()
     return wxEmptyString;
 }
 
-void wxComboBox::SetStringSelection(wxString& selection)
+void wxComboBox::SetStringSelection(const wxString& selection)
 {
 }