diff --git a/src/prefs/ModulePrefs.cpp b/src/prefs/ModulePrefs.cpp
index ddd8f69cd..676d6ff0a 100644
--- a/src/prefs/ModulePrefs.cpp
+++ b/src/prefs/ModulePrefs.cpp
@@ -138,7 +138,7 @@ bool ModulePrefs::Apply()
 
 
 // static function that tells us about a module.
-int ModulePrefs::GetModuleStatus( wxString fname ){
+int ModulePrefs::GetModuleStatus(const wxString &fname){
    // Default status is NEW module, and we will ask once.
    int iStatus = kModuleNew;
 
@@ -152,7 +152,7 @@ int ModulePrefs::GetModuleStatus( wxString fname ){
    return iStatus;
 }
 
-void ModulePrefs::SetModuleStatus( wxString fname, int iStatus ){
+void ModulePrefs::SetModuleStatus(const wxString &fname, int iStatus){
    wxString ShortName = wxFileName( fname ).GetName();
    wxString PrefName = wxString( wxT("/Module/") ) + ShortName.Lower();
    gPrefs->Write( PrefName, iStatus );
diff --git a/src/prefs/ModulePrefs.h b/src/prefs/ModulePrefs.h
index 09d80a1d2..2c042d93d 100644
--- a/src/prefs/ModulePrefs.h
+++ b/src/prefs/ModulePrefs.h
@@ -38,8 +38,8 @@ class ModulePrefs:public PrefsPanel
    ~ModulePrefs();
    virtual bool Apply();
 
-   static int GetModuleStatus( wxString fname );
-   static void SetModuleStatus( wxString fname, int iStatus );
+   static int GetModuleStatus( const wxString &fname );
+   static void SetModuleStatus( const wxString &fname, int iStatus );
 
  private:
    void GetAllModuleStatuses();
diff --git a/src/prefs/PrefsDialog.cpp b/src/prefs/PrefsDialog.cpp
index c7749ecb0..2dfe0602a 100644
--- a/src/prefs/PrefsDialog.cpp
+++ b/src/prefs/PrefsDialog.cpp
@@ -448,7 +448,7 @@ void PrefsDialog::OnOK(wxCommandEvent & WXUNUSED(event))
    EndModal(true);
 }
 
-void PrefsDialog::SelectPageByName(wxString pageName)
+void PrefsDialog::SelectPageByName(const wxString &pageName)
 {
    if (mCategories) {
       size_t n = mCategories->GetPageCount();
diff --git a/src/prefs/PrefsDialog.h b/src/prefs/PrefsDialog.h
index 42bbf89f1..13c7092fa 100644
--- a/src/prefs/PrefsDialog.h
+++ b/src/prefs/PrefsDialog.h
@@ -61,7 +61,7 @@ class PrefsDialog:public wxDialog
    void OnApply(wxCommandEvent & e);
    void OnTreeKeyDown(wxTreeEvent & e); // Used to dismiss the dialog when enter is pressed with focus on tree
 
-   void SelectPageByName(wxString pageName);
+   void SelectPageByName(const wxString &pageName);
 
    // Accessor to help implementations of SavePreferredPage(),
    // such as by saving a preference after DoModal() returns
diff --git a/src/prefs/PrefsPanel.h b/src/prefs/PrefsPanel.h
index 77da3a042..245f2f122 100644
--- a/src/prefs/PrefsPanel.h
+++ b/src/prefs/PrefsPanel.h
@@ -43,7 +43,7 @@ ThemePrefs.
 class PrefsPanel:public wxPanel
 {
  public:
-   PrefsPanel(wxWindow * parent, wxString title)
+   PrefsPanel(wxWindow * parent, const wxString &title)
    :  wxPanel(parent, wxID_ANY)
    {
       SetLabel(title);     // Provide visual label