diff --git a/opm/core/WellCollection.cpp b/opm/core/WellCollection.cpp
index 1fd954d4c..b09e47df2 100644
--- a/opm/core/WellCollection.cpp
+++ b/opm/core/WellCollection.cpp
@@ -69,7 +69,7 @@ namespace Opm
         return leaf_nodes_;
     }
 
-    WellsGroupInterface* WellCollection::findNode(std::string name)
+    WellsGroupInterface* WellCollection::findNode(const std::string& name)
     {
 
         for (size_t i = 0; i < roots_.size(); i++) {
@@ -81,7 +81,7 @@ namespace Opm
         return NULL;
     }
     
-    const WellsGroupInterface* WellCollection::findNode(std::string name) const
+    const WellsGroupInterface* WellCollection::findNode(const std::string& name) const
     {
 
         for (size_t i = 0; i < roots_.size(); i++) {
diff --git a/opm/core/WellCollection.hpp b/opm/core/WellCollection.hpp
index 640f26670..595ef7ce7 100644
--- a/opm/core/WellCollection.hpp
+++ b/opm/core/WellCollection.hpp
@@ -79,12 +79,12 @@ namespace Opm
         /// Finds the group with the given name.
         /// \param[in] the name of the group
         /// \return the pointer to the group if found, NULL otherwise
-        WellsGroupInterface* findNode(std::string name);
+        WellsGroupInterface* findNode(const std::string& name);
         
         /// Finds the group with the given name.
         /// \param[in] the name of the group
         /// \return the pointer to the group if found, NULL otherwise
-        const WellsGroupInterface* findNode(std::string name) const;
+        const WellsGroupInterface* findNode(const std::string& name) const;
         
     private:
         // To account for the possibility of a forest
diff --git a/opm/core/WellsGroup.cpp b/opm/core/WellsGroup.cpp
index a048e5017..6c8649a63 100644
--- a/opm/core/WellsGroup.cpp
+++ b/opm/core/WellsGroup.cpp
@@ -90,7 +90,7 @@ namespace Opm
         return injection_specification_;
     }
 
-    WellsGroupInterface* WellsGroup::findGroup(std::string name_of_node)
+    WellsGroupInterface* WellsGroup::findGroup(const std::string& name_of_node)
     {
         if (name() == name_of_node) {
             return this;
@@ -288,7 +288,7 @@ namespace Opm
         return true;
     }
 
-    WellsGroupInterface* WellNode::findGroup(std::string name_of_node)
+    WellsGroupInterface* WellNode::findGroup(const std::string& name_of_node)
     {
         if (name() == name_of_node) {
             return this;
diff --git a/opm/core/WellsGroup.hpp b/opm/core/WellsGroup.hpp
index bfc25c406..5cf1ae74d 100644
--- a/opm/core/WellsGroup.hpp
+++ b/opm/core/WellsGroup.hpp
@@ -54,7 +54,7 @@ namespace Opm
         
         /// \returns the pointer to the WellsGroupInterface with the given name. NULL if 
         ///          the name is not found.a
-        virtual WellsGroupInterface* findGroup(std::string name_of_node) = 0;
+        virtual WellsGroupInterface* findGroup(const std::string& name_of_node) = 0;
 
         /// Sets the parent
         /// \param[in] parent the pointer to the parent
@@ -125,7 +125,7 @@ namespace Opm
                    ProductionSpecification prod_spec,
                    InjectionSpecification inj_spec);
 
-        virtual WellsGroupInterface* findGroup(std::string name_of_node);
+        virtual WellsGroupInterface* findGroup(const std::string& name_of_node);
 
         void addChild(std::tr1::shared_ptr<WellsGroupInterface> child);
         
@@ -154,7 +154,7 @@ namespace Opm
                  ProductionSpecification prod_spec,
                 InjectionSpecification inj_spec);
 
-        virtual WellsGroupInterface* findGroup(std::string name_of_node);
+        virtual WellsGroupInterface* findGroup(const std::string& name_of_node);
         virtual bool conditionsMet(const std::vector<double>& well_bhp,
                                    const std::vector<double>& well_rate,
                                    WellPhasesSummed& summed_phases,