diff --git a/apps/openmw/mwbase/mechanicsmanager.hpp b/apps/openmw/mwbase/mechanicsmanager.hpp
index 967504552d..1fe922a47b 100644
--- a/apps/openmw/mwbase/mechanicsmanager.hpp
+++ b/apps/openmw/mwbase/mechanicsmanager.hpp
@@ -230,7 +230,7 @@ namespace MWBase
             virtual bool isReadyToBlock (const MWWorld::Ptr& ptr) const = 0;
             virtual bool isAttackingOrSpell(const MWWorld::Ptr &ptr) const = 0;
 
-            virtual void castSpell(const MWWorld::Ptr& ptr, const std::string spellId, bool manualSpell) = 0;
+            virtual void castSpell(const MWWorld::Ptr& ptr, const std::string& spellId, bool manualSpell) = 0;
 
             virtual void processChangedSettings (const std::set< std::pair<std::string, std::string> >& settings) = 0;
 
diff --git a/apps/openmw/mwmechanics/actors.cpp b/apps/openmw/mwmechanics/actors.cpp
index 87f462d6ff..e62d686ee2 100644
--- a/apps/openmw/mwmechanics/actors.cpp
+++ b/apps/openmw/mwmechanics/actors.cpp
@@ -1667,7 +1667,7 @@ namespace MWMechanics
         }
     }
 
-    void Actors::castSpell(const MWWorld::Ptr& ptr, const std::string spellId, bool manualSpell)
+    void Actors::castSpell(const MWWorld::Ptr& ptr, const std::string& spellId, bool manualSpell)
     {
         PtrActorMap::iterator iter = mActors.find(ptr);
         if(iter != mActors.end())
diff --git a/apps/openmw/mwmechanics/actors.hpp b/apps/openmw/mwmechanics/actors.hpp
index 0ae9687578..171b45e270 100644
--- a/apps/openmw/mwmechanics/actors.hpp
+++ b/apps/openmw/mwmechanics/actors.hpp
@@ -101,7 +101,7 @@ namespace MWMechanics
 
             void resurrect (const MWWorld::Ptr& ptr);
 
-            void castSpell(const MWWorld::Ptr& ptr, const std::string spellId, bool manualSpell=false);
+            void castSpell(const MWWorld::Ptr& ptr, const std::string& spellId, bool manualSpell=false);
 
             void updateActor(const MWWorld::Ptr &old, const MWWorld::Ptr& ptr);
             ///< Updates an actor with a new Ptr
diff --git a/apps/openmw/mwmechanics/character.cpp b/apps/openmw/mwmechanics/character.cpp
index 54c951187f..d5a1d46a88 100644
--- a/apps/openmw/mwmechanics/character.cpp
+++ b/apps/openmw/mwmechanics/character.cpp
@@ -2852,7 +2852,7 @@ void CharacterController::setAttackingOrSpell(bool attackingOrSpell)
     mAttackingOrSpell = attackingOrSpell;
 }
 
-void CharacterController::castSpell(const std::string spellId, bool manualSpell)
+void CharacterController::castSpell(const std::string& spellId, bool manualSpell)
 {
     mAttackingOrSpell = true;
     mCastingManualSpell = manualSpell;
diff --git a/apps/openmw/mwmechanics/character.hpp b/apps/openmw/mwmechanics/character.hpp
index 3f7fa4e1bd..adeaa739af 100644
--- a/apps/openmw/mwmechanics/character.hpp
+++ b/apps/openmw/mwmechanics/character.hpp
@@ -286,7 +286,7 @@ public:
 
     void setVisibility(float visibility);
     void setAttackingOrSpell(bool attackingOrSpell);
-    void castSpell(const std::string spellId, bool manualSpell=false);
+    void castSpell(const std::string& spellId, bool manualSpell=false);
     void setAIAttackType(const std::string& attackType);
     static void setAttackTypeRandomly(std::string& attackType);
 
diff --git a/apps/openmw/mwmechanics/mechanicsmanagerimp.cpp b/apps/openmw/mwmechanics/mechanicsmanagerimp.cpp
index 7101139821..352a6cca43 100644
--- a/apps/openmw/mwmechanics/mechanicsmanagerimp.cpp
+++ b/apps/openmw/mwmechanics/mechanicsmanagerimp.cpp
@@ -251,7 +251,7 @@ namespace MWMechanics
             mObjects.addObject(ptr);
     }
 
-    void MechanicsManager::castSpell(const MWWorld::Ptr& ptr, const std::string spellId, bool manualSpell)
+    void MechanicsManager::castSpell(const MWWorld::Ptr& ptr, const std::string& spellId, bool manualSpell)
     {
         if(ptr.getClass().isActor())
             mActors.castSpell(ptr, spellId, manualSpell);
diff --git a/apps/openmw/mwmechanics/mechanicsmanagerimp.hpp b/apps/openmw/mwmechanics/mechanicsmanagerimp.hpp
index 3f2c3f5e98..0b1d7377b2 100644
--- a/apps/openmw/mwmechanics/mechanicsmanagerimp.hpp
+++ b/apps/openmw/mwmechanics/mechanicsmanagerimp.hpp
@@ -186,7 +186,7 @@ namespace MWMechanics
             /// Is \a ptr casting spell or using weapon now?
             bool isAttackingOrSpell(const MWWorld::Ptr &ptr) const override;
 
-            void castSpell(const MWWorld::Ptr& ptr, const std::string spellId, bool manualSpell=false) override;
+            void castSpell(const MWWorld::Ptr& ptr, const std::string& spellId, bool manualSpell=false) override;
 
             void processChangedSettings(const Settings::CategorySettingVector& settings) override;
 
diff --git a/components/misc/stringops.hpp b/components/misc/stringops.hpp
index 48deaa9991..59768b92ac 100644
--- a/components/misc/stringops.hpp
+++ b/components/misc/stringops.hpp
@@ -66,7 +66,7 @@ public:
         return ch;
     }
 
-    static std::string lowerCaseUtf8(const std::string str)
+    static std::string lowerCaseUtf8(const std::string& str)
     {
         if (str.empty())
             return str;
diff --git a/components/resource/bulletshapemanager.cpp b/components/resource/bulletshapemanager.cpp
index ad37eda0dd..b1b0f74176 100644
--- a/components/resource/bulletshapemanager.cpp
+++ b/components/resource/bulletshapemanager.cpp
@@ -45,9 +45,9 @@ struct GetTriangleFunctor
     }
 
 #if OSG_MIN_VERSION_REQUIRED(3,5,6)
-    void inline operator()( const osg::Vec3 v1, const osg::Vec3 v2, const osg::Vec3 v3 )
+    void inline operator()( const osg::Vec3& v1, const osg::Vec3& v2, const osg::Vec3& v3 )
 #else
-    void inline operator()( const osg::Vec3 v1, const osg::Vec3 v2, const osg::Vec3 v3, bool _temp )
+    void inline operator()( const osg::Vec3& v1, const osg::Vec3& v2, const osg::Vec3& v3, bool _temp )
 #endif
     {
         if (mTriMesh)
diff --git a/components/resource/keyframemanager.cpp b/components/resource/keyframemanager.cpp
index d7eeeeb971..69986fbcd9 100644
--- a/components/resource/keyframemanager.cpp
+++ b/components/resource/keyframemanager.cpp
@@ -106,7 +106,7 @@ namespace Resource
         return time;
     }
 
-    std::string RetrieveAnimationsVisitor::changeFileExtension(const std::string file, const std::string ext)
+    std::string RetrieveAnimationsVisitor::changeFileExtension(const std::string& file, const std::string& ext)
     {
         size_t extPos = file.find_last_of('.');
         if (extPos != std::string::npos && extPos+1 < file.size())
diff --git a/components/resource/keyframemanager.hpp b/components/resource/keyframemanager.hpp
index 87a20b97a5..75c9cc6ff4 100644
--- a/components/resource/keyframemanager.hpp
+++ b/components/resource/keyframemanager.hpp
@@ -22,7 +22,7 @@ namespace Resource
 
         private:
 
-            std::string changeFileExtension(const std::string file, const std::string ext);
+            std::string changeFileExtension(const std::string& file, const std::string& ext);
             std::string parseTextKey(const std::string& line);
             double parseTimeSignature(const std::string& line);
 
diff --git a/components/sceneutil/util.cpp b/components/sceneutil/util.cpp
index 1fe3685726..ad5daa6e02 100644
--- a/components/sceneutil/util.cpp
+++ b/components/sceneutil/util.cpp
@@ -200,7 +200,7 @@ float makeOsgColorComponent(unsigned int value, unsigned int shift)
     return float((value >> shift) & 0xFFu) / 255.0f;
 }
 
-bool hasUserDescription(const osg::Node* node, const std::string pattern)
+bool hasUserDescription(const osg::Node* node, const std::string& pattern)
 {
     if (node == nullptr)
         return false;
diff --git a/components/sceneutil/util.hpp b/components/sceneutil/util.hpp
index 8103ed87a8..151f65db79 100644
--- a/components/sceneutil/util.hpp
+++ b/components/sceneutil/util.hpp
@@ -58,7 +58,7 @@ namespace SceneUtil
 
     float makeOsgColorComponent (unsigned int value, unsigned int shift);
 
-    bool hasUserDescription(const osg::Node* node, const std::string pattern);
+    bool hasUserDescription(const osg::Node* node, const std::string& pattern);
 
     osg::ref_ptr<GlowUpdater> addEnchantedGlow(osg::ref_ptr<osg::Node> node, Resource::ResourceSystem* resourceSystem, osg::Vec4f glowColor, float glowDuration=-1);