diff --git a/src/App/Extension.cpp b/src/App/Extension.cpp
index 4a348b53c..35637df6d 100644
--- a/src/App/Extension.cpp
+++ b/src/App/Extension.cpp
@@ -113,7 +113,7 @@ std::string Extension::name() const {
     std::string temp(m_extensionType.getName());
     std::string::size_type pos = temp.find_last_of(":");
 
-    if(pos != std::string::npos) 
+    if(pos != std::string::npos)
         return temp.substr(pos+1);
     else
         return std::string();
diff --git a/src/App/Extension.h b/src/App/Extension.h
index fe68c5862..1dfc8dab8 100644
--- a/src/App/Extension.h
+++ b/src/App/Extension.h
@@ -255,8 +255,8 @@ public:
     
     /** @name Persistance */
     //@{
-    virtual void extensionSave(Base::Writer&) const {};
-    virtual void extensionRestore(Base::XMLReader&) {};
+    virtual void extensionSave(Base::Writer&) const {}
+    virtual void extensionRestore(Base::XMLReader&) {}
     //@}
     
     /** @name TypeHandling */
diff --git a/src/App/ExtensionContainer.cpp b/src/App/ExtensionContainer.cpp
index 47f100555..1b5ef4f49 100644
--- a/src/App/ExtensionContainer.cpp
+++ b/src/App/ExtensionContainer.cpp
@@ -83,7 +83,7 @@ bool ExtensionContainer::hasExtension(Base::Type t) const {
     return true;
 }
 
-bool ExtensionContainer::hasExtension(std::string name) const {
+bool ExtensionContainer::hasExtension(const std::string& name) const {
 
     //and for types derived from it, as they can be cast to the extension
     for(auto entry : _extensions) {            
@@ -115,7 +115,7 @@ bool ExtensionContainer::hasExtensions() const {
     return !_extensions.empty();
 }
 
-Extension* ExtensionContainer::getExtension(std::string name) {
+Extension* ExtensionContainer::getExtension(const std::string& name) {
 
     //and for types derived from it, as they can be cast to the extension
     for(auto entry : _extensions) {            
diff --git a/src/App/ExtensionContainer.h b/src/App/ExtensionContainer.h
index 303f0e27c..2c81784ae 100644
--- a/src/App/ExtensionContainer.h
+++ b/src/App/ExtensionContainer.h
@@ -125,10 +125,10 @@ public:
 
     void registerExtension(Base::Type extension, App::Extension* ext);
     bool hasExtension(Base::Type) const; //returns first of type (or derived from) and throws otherwise
-    bool hasExtension(std::string name) const; //this version does not check derived classes
+    bool hasExtension(const std::string& name) const; //this version does not check derived classes
     bool hasExtensions() const;
     App::Extension* getExtension(Base::Type);  //returns first of type (or derived from) and throws otherwise
-    App::Extension* getExtension(std::string name); //this version does not check derived classes
+    App::Extension* getExtension(const std::string& name); //this version does not check derived classes
     
     //returns first of type (or derived from) and throws otherwise
     template<typename ExtensionT>