diff --git a/python/templates/MutableObject.cc.jinja2 b/python/templates/MutableObject.cc.jinja2
index d94b4f32c..329a0f830 100644
--- a/python/templates/MutableObject.cc.jinja2
+++ b/python/templates/MutableObject.cc.jinja2
@@ -12,8 +12,6 @@
 #include "nlohmann/json.hpp"
 #endif
 
-#include <ostream>
-
 {{ utils.namespace_open(class.namespace) }}
 
 {{ macros.constructors_destructors(class.bare_type, Members, multi_relations=OneToManyRelations + VectorMembers, prefix='Mutable') }}
diff --git a/python/templates/Obj.cc.jinja2 b/python/templates/Obj.cc.jinja2
index 1f935ca46..b127fcce7 100644
--- a/python/templates/Obj.cc.jinja2
+++ b/python/templates/Obj.cc.jinja2
@@ -57,7 +57,7 @@
 {%- endwith %}
 
 {% for relation in OneToOneRelations %}
-  if (m_{{ relation.name }}) delete m_{{ relation.name }};
+  delete m_{{ relation.name }};
 {% endfor %}
 }
 {%- endif %}
diff --git a/python/templates/macros/declarations.jinja2 b/python/templates/macros/declarations.jinja2
index 5ef5b8707..a329c599a 100644
--- a/python/templates/macros/declarations.jinja2
+++ b/python/templates/macros/declarations.jinja2
@@ -121,7 +121,7 @@
 {% macro single_relation_setters(relations, get_syntax) %}
 {% for relation in relations %}
   /// Set the {{ relation.description }}
-  void {{ relation.setter_name(get_syntax) }}({{ relation.full_type }} value);
+  void {{ relation.setter_name(get_syntax) }}(const {{ relation.full_type }}& value);
 {% endfor %}
 {%- endmacro %}
 
diff --git a/python/templates/macros/implementations.jinja2 b/python/templates/macros/implementations.jinja2
index d3f367fdf..c1c8221bd 100644
--- a/python/templates/macros/implementations.jinja2
+++ b/python/templates/macros/implementations.jinja2
@@ -123,10 +123,8 @@ const {{ relation.full_type }} {{ class_type }}::{{ relation.getter_name(get_syn
 {% macro single_relation_setters(class, relations, get_syntax, prefix='') %}
 {% set class_type = prefix + class.bare_type %}
 {% for relation in relations %}
-void {{ class_type }}::{{ relation.setter_name(get_syntax) }}({{ relation.full_type }} value) {
-  if (m_obj->m_{{ relation.name }}) {
-    delete m_obj->m_{{ relation.name }};
-  }
+void {{ class_type }}::{{ relation.setter_name(get_syntax) }}(const {{ relation.full_type }}& value) {
+  delete m_obj->m_{{ relation.name }};
   m_obj->m_{{ relation.name }} = new {{ relation.full_type }}(value);
 }
 
@@ -182,10 +180,7 @@ podio::RelationRange<{{ relation.full_type }}> {{ class_type }}::{{ relation.get
 {% macro common_object_funcs(class, prefix='') %}
 {% set full_type = prefix + class.bare_type %}
 bool {{ full_type }}::isAvailable() const {
-  if (m_obj) {
-    return true;
-  }
-  return false;
+  return m_obj;
 }
 
 const podio::ObjectID {{ full_type }}::getObjectID() const {
diff --git a/python/templates/macros/utils.jinja2 b/python/templates/macros/utils.jinja2
index 56511a6fe..c2686222a 100644
--- a/python/templates/macros/utils.jinja2
+++ b/python/templates/macros/utils.jinja2
@@ -30,7 +30,6 @@ namespace {{ nsp }} {
 #include "{{ incfolder }}Mutable{{ type }}.h"
 #include "{{ incfolder }}{{ type }}Obj.h"
 #include "{{ incfolder }}{{ type }}Data.h"
-#include "{{ incfolder }}{{ type }}Collection.h"
 {%- endmacro %}