diff --git a/src/sbml/validator/constraints/AssignmentCycles.cpp b/src/sbml/validator/constraints/AssignmentCycles.cpp
index fe7b549df..7e6a52b8b 100644
--- a/src/sbml/validator/constraints/AssignmentCycles.cpp
+++ b/src/sbml/validator/constraints/AssignmentCycles.cpp
@@ -84,7 +84,7 @@ AssignmentCycles::~AssignmentCycles ()
 void
 AssignmentCycles::check_ (const Model& m, const Model& object)
 {
-  // this rule ony applies in l2v2 and beyond
+  // this rule only applies in l2v2 and beyond
   if (object.getLevel() == 1 
     || (object.getLevel() == 2 && object.getVersion() == 1))
     return;
@@ -271,21 +271,19 @@ AssignmentCycles::determineAllDependencies()
 
 
 bool 
-AssignmentCycles::alreadyExistsInMap(IdMap map, 
-                                     pair<const std::string, std::string> dependency)
+AssignmentCycles::alreadyExistsInMap(IdMap& map, 
+                                     const pair<const std::string, std::string>& dependency) const
 {
-  bool exists = false;
-
   IdIter it;
   
-  for (it = map.begin(); it != map.end(); it++)
+  for (it = map.begin(); it != map.end(); ++it)
   {
     if (((*it).first == dependency.first)
       && ((*it).second == dependency.second))
-      exists = true;
+      return true;
   }
 
-  return exists;
+  return false;
 }
 
   
diff --git a/src/sbml/validator/constraints/AssignmentCycles.h b/src/sbml/validator/constraints/AssignmentCycles.h
index b854ab501..0466d304f 100644
--- a/src/sbml/validator/constraints/AssignmentCycles.h
+++ b/src/sbml/validator/constraints/AssignmentCycles.h
@@ -92,8 +92,8 @@ class AssignmentCycles: public TConstraint<Model>
 
 
   /* helper function to check if a pair already exists */
-  bool alreadyExistsInMap(IdMap map, 
-                          std::pair<const std::string, std::string> dependency);
+  bool alreadyExistsInMap(IdMap& map, 
+                          const std::pair<const std::string, std::string>& dependency) const;
 
   
   /* check for explicit use of original variable */