diff --git a/src/OpenMesh/Tools/Subdivider/Adaptive/Composite/CompositeT.hh b/src/OpenMesh/Tools/Subdivider/Adaptive/Composite/CompositeT.hh
index 779dc282..2d5d0c35 100644
--- a/src/OpenMesh/Tools/Subdivider/Adaptive/Composite/CompositeT.hh
+++ b/src/OpenMesh/Tools/Subdivider/Adaptive/Composite/CompositeT.hh
@@ -256,15 +256,15 @@ protected:
 protected: // helper
 
   // get current generation from state
-  state_t generation(state_t _s) { return _s-(_s % n_rules()); }
-  state_t generation( VH _vh ) { return generation(mesh_.data(_vh).state()); }
-  state_t generation( EH _eh ) { return generation(mesh_.data(_eh).state()); }
-  state_t generation( FH _fh ) { return generation(mesh_.data(_fh).state()); }
+  state_t generation(state_t _s) const { return _s-(_s % n_rules()); }
+  state_t generation( VH _vh ) const  { return generation(mesh_.data(_vh).state()); }
+  state_t generation( EH _eh ) const { return generation(mesh_.data(_eh).state()); }
+  state_t generation( FH _fh ) const { return generation(mesh_.data(_fh).state()); }
 
 private:
 
   // short cuts
-  Rule* t_rule() { return subdiv_rule_;           }
+  Rule* t_rule() const { return subdiv_rule_;           }
   Rule* f_rule() { return rule_sequence_.front(); }
   Rule* l_rule() { return rule_sequence_.back();  }
 
diff --git a/src/OpenMesh/Tools/Subdivider/Adaptive/Composite/RuleInterfaceT.hh b/src/OpenMesh/Tools/Subdivider/Adaptive/Composite/RuleInterfaceT.hh
index 90139af3..dc133148 100644
--- a/src/OpenMesh/Tools/Subdivider/Adaptive/Composite/RuleInterfaceT.hh
+++ b/src/OpenMesh/Tools/Subdivider/Adaptive/Composite/RuleInterfaceT.hh
@@ -358,12 +358,12 @@ protected:
   Self* prev_rule() { return prev_rule_; }
 
   void  set_subdiv_rule(Self*& _n) { subdiv_rule_ = _n; }
-  Self* subdiv_rule() { return subdiv_rule_; }
+  Self* subdiv_rule() const { return subdiv_rule_; }
 
   void set_number(int _n) { number_ = _n; }
 
   void set_n_rules(int _n) { n_rules_ = _n; }
-  int  n_rules() { return n_rules_; }
+  int  n_rules() const { return n_rules_; }
 
   void set_subdiv_type(int _n) 
   { assert(_n == 3 || _n == 4); subdiv_type_ = _n; }