diff --git a/conandata.yml b/conandata.yml
index 2450b11..d5c7d03 100644
--- a/conandata.yml
+++ b/conandata.yml
@@ -1,3 +1,3 @@
-version: "5.11.1-alpha.0"
+version: "5.12.0"
 requirements:
-  - "savitar/5.11.0-alpha.0"
+  - "savitar/5.12.0"
diff --git a/python/MeshData.sip b/python/MeshData.sip
index 3beffd7..c508830 100644
--- a/python/MeshData.sip
+++ b/python/MeshData.sip
@@ -10,7 +10,7 @@ public:
     MeshData();
     virtual ~MeshData();
     bytearray getVerticesAsBytes();
-    bytearray getFacesAsBytes();
+    bytearray getFacesAsBytes() const;
 
     bytearray getFlatVerticesAsBytes();
 
diff --git a/python/Scene.sip b/python/Scene.sip
index a2a552c..f00ae10 100644
--- a/python/Scene.sip
+++ b/python/Scene.sip
@@ -10,7 +10,7 @@ public:
     Scene();
     virtual ~Scene();
 
-    std::vector<SceneNode*> getSceneNodes();
+    const std::vector<SceneNode*>& getSceneNodes() const;
     std::vector<SceneNode*> getAllSceneNodes();
 
     void addSceneNode(SceneNode* node /Transfer/);
@@ -21,7 +21,7 @@ public:
     void setMetaDataEntry(const std::string& key, const std::string& value, const std::string& type);
     void setMetaDataEntry(const std::string& key, const std::string& value, const std::string& type, const bool preserve);
 
-    std::string getUnit();
+    const std::string& getUnit() const;
     void setUnit(std::string unit);
 };
 
diff --git a/python/SceneNode.sip b/python/SceneNode.sip
index 48c9547..2229f97 100644
--- a/python/SceneNode.sip
+++ b/python/SceneNode.sip
@@ -10,14 +10,14 @@ public:
     SceneNode();
     virtual ~SceneNode();
 
-    MeshData& getMeshData();
+    const MeshData& getMeshData() const;
 
-    std::vector<SceneNode*> getChildren();
+    const std::vector<SceneNode*>& getChildren() const;
 
-    std::string getTransformation();
-    void setTransformation(std::string);
+    const std::string& getTransformation() const;
+    void setTransformation(const std::string&);
     
-    std::string getName();
+    const std::string& getName() const;
     void setName(std::string name);
 
     int getId();