diff --git a/clientgui/BOINCGUIApp.cpp b/clientgui/BOINCGUIApp.cpp
index 408925c3203..df9aa21bade 100644
--- a/clientgui/BOINCGUIApp.cpp
+++ b/clientgui/BOINCGUIApp.cpp
@@ -205,17 +205,22 @@ bool CBOINCGUIApp::OnInit() {
 #endif
     m_pConfig->Read(wxT("DisableAutoStart"), &m_iBOINCMGRDisableAutoStart, 0L);
     m_pConfig->Read(wxT("LanguageISO"), &m_strISOLanguageCode, wxT(""));
-#ifdef __WXMAC__   // wxWidgets System language detection does not work on Mac
     m_bUseDefaultLocale = false;
-#else
     bool bUseDefaultLocaleDefault = false;
+#ifdef __WXMAC__   // wxLocale::GetLanguageInfo(wxLANGUAGE_DEFAULT) does not work on Mac
+    wxLocale *defaultLocale = new wxLocale;
+    defaultLocale->Init(wxLANGUAGE_DEFAULT);
+    wxString defaultLanguageCode = defaultLocale->GetCanonicalName();
+    bUseDefaultLocaleDefault = m_strISOLanguageCode == defaultLanguageCode;
+    delete defaultLocale;
+#else
     const wxLanguageInfo *defaultLanguageInfo = wxLocale::GetLanguageInfo(wxLANGUAGE_DEFAULT);
     if (defaultLanguageInfo != NULL) {
         // Migration: assume a selected language code that matches the system default means "auto select"
         bUseDefaultLocaleDefault = m_strISOLanguageCode == defaultLanguageInfo->CanonicalName;;
     }
-    m_pConfig->Read(wxT("UseDefaultLocale"), &m_bUseDefaultLocale, bUseDefaultLocaleDefault);
 #endif
+    m_pConfig->Read(wxT("UseDefaultLocale"), &m_bUseDefaultLocale, bUseDefaultLocaleDefault);
     m_pConfig->Read(wxT("GUISelection"), &m_iGUISelected, BOINC_SIMPLEGUI);
     m_pConfig->Read(wxT("EventLogOpen"), &bOpenEventLog);
     m_pConfig->Read(wxT("RunDaemon"), &m_bRunDaemon, 1L);
@@ -953,7 +958,6 @@ void CBOINCGUIApp::InitSupportedLanguages() {
     wxLayoutDirection uiLayoutDirection = pLIui ? pLIui->LayoutDirection : wxLayout_Default;
     GUI_SUPPORTED_LANG newItem;
 
-#ifndef __WXMAC__   // wxWidgets System language detection does not work on Mac
     // CDlgOptions depends on "Auto" being the first item in the list
     // if
     newItem.Language = wxLANGUAGE_DEFAULT;
@@ -973,11 +977,11 @@ void CBOINCGUIApp::InitSupportedLanguages() {
         newItem.Label += LRM + strAutoEnglish + LRM;
     }
     m_astrLanguages.push_back(newItem);
-#endif
 
     // Add known locales to the list
     for (int langID = wxLANGUAGE_UNKNOWN+1; langID < wxLANGUAGE_USER_DEFINED; ++langID) {
         const wxLanguageInfo* pLI = wxLocale::GetLanguageInfo(langID);
+        if (pLI == NULL) continue;
         wxString lang_region = pLI->CanonicalName.BeforeFirst('@');
         wxString lang = lang_region.BeforeFirst('_');
         wxString script = pLI->CanonicalName.AfterFirst('@');
diff --git a/clientgui/DlgOptions.cpp b/clientgui/DlgOptions.cpp
index 22bbe9b7d05..9ec4810d052 100644
--- a/clientgui/DlgOptions.cpp
+++ b/clientgui/DlgOptions.cpp
@@ -623,8 +623,6 @@ bool CDlgOptions::ReadSettings() {
     wxASSERT(wxDynamicCast(pDoc, CMainDocument));
     wxASSERT(wxDynamicCast(pFrame, CBOINCBaseFrame));
 
-// wxWidgets System language detection does not work on Mac
-// so we always set UseDefaultLocale() to false on Mac
     // General Tab
     if (wxGetApp().UseDefaultLocale()) {
         // CBOINCGUIApp::InitSupportedLanguages() ensures "Auto" is the first item in the list
@@ -734,7 +732,7 @@ bool CDlgOptions::SaveSettings() {
     CSkinAdvanced*      pSkinAdvanced = wxGetApp().GetSkinManager()->GetAdvanced();
     long                lBuffer = 0;
     wxString            strBuffer = wxEmptyString;
-
+    const wxLanguageInfo *newLanguageInfo = NULL;
 
     wxASSERT(pDoc);
     wxASSERT(pFrame);
@@ -750,14 +748,19 @@ bool CDlgOptions::SaveSettings() {
     int selLangIdx = m_LanguageSelectionCtrl->GetSelection();
     if (selLangIdx == 0) {
         // CBOINCGUIApp::InitSupportedLanguages() ensures "Auto" is the first item in the list
-        newLangCode = wxLocale::GetLanguageInfo(wxLANGUAGE_DEFAULT)->CanonicalName;
+        newLanguageInfo = wxLocale::GetLanguageInfo(wxLANGUAGE_DEFAULT);
+        // wxLocale::GetLanguageInfo(wxLANGUAGE_DEFAULT) may return NULL on Macintosh
+        newLangCode = wxEmptyString;
     } else if (selLangIdx > 0) {
         const std::vector<GUI_SUPPORTED_LANG>& langs = wxGetApp().GetSupportedLanguages();
         if (selLangIdx < langs.size()) {
             const GUI_SUPPORTED_LANG& selLang = langs[selLangIdx];
-            newLangCode = wxLocale::GetLanguageInfo(selLang.Language)->CanonicalName;
+            newLanguageInfo = wxLocale::GetLanguageInfo(selLang.Language);
         }
     }
+    if (newLanguageInfo) {
+        newLangCode = newLanguageInfo->CanonicalName;
+    }
     if (newLangCode != oldLangCode) {
         wxString strDialogTitle;
         wxString strDialogMessage;