diff --git a/src/osx/cocoa/combobox.mm b/src/osx/cocoa/combobox.mm
index 1666c33b83..d98f0a331e 100644
--- a/src/osx/cocoa/combobox.mm
+++ b/src/osx/cocoa/combobox.mm
@@ -95,9 +95,21 @@ int wxNSComboBoxControl::GetSelectedItem() const
 
 void wxNSComboBoxControl::SetSelectedItem(int item)
 {
-    wxASSERT_MSG(item >= 0 && item < [m_comboBox numberOfItems], "Inavlid item index.");
     SendEvents(false);
-    [m_comboBox selectItemAtIndex: item];
+
+    if ( item != wxNOT_FOUND )
+    {
+        wxASSERT_MSG( item >= 0 && item < [m_comboBox numberOfItems],
+                      "Inavlid item index." );
+        [m_comboBox selectItemAtIndex: item];
+    }
+    else // remove current selection (if we have any)
+    {
+        const int sel = GetSelectedItem();
+        if ( sel != wxNOT_FOUND )
+            [m_comboBox deselectItemAtIndex:sel];
+    }
+
     SendEvents(true);
 }
 
diff --git a/src/osx/combobox_osx.cpp b/src/osx/combobox_osx.cpp
index 214bdbdff4..8ab1cf9c1e 100644
--- a/src/osx/combobox_osx.cpp
+++ b/src/osx/combobox_osx.cpp
@@ -186,12 +186,15 @@ int wxComboBox::FindString(const wxString& s, bool bCase) const
 
 wxString wxComboBox::GetString(unsigned int n) const
 {
+    wxCHECK_MSG( n < GetCount(), wxString(), "Invalid combobox index" );
+
     return GetComboPeer()->GetStringAtIndex(n);
 }
 
 wxString wxComboBox::GetStringSelection() const
 {
-    return GetString(GetSelection());
+    const int sel = GetSelection();
+    return sel == wxNOT_FOUND ? wxString() : GetString(sel);
 }
 
 void wxComboBox::SetString(unsigned int n, const wxString& s)