diff --git a/opm/parser/eclipse/EclipseState/Schedule/CompletionSet.cpp b/opm/parser/eclipse/EclipseState/Schedule/CompletionSet.cpp
index 25172df7d..a4b9eb8f3 100644
--- a/opm/parser/eclipse/EclipseState/Schedule/CompletionSet.cpp
+++ b/opm/parser/eclipse/EclipseState/Schedule/CompletionSet.cpp
@@ -55,8 +55,8 @@ namespace Opm {
     }
 
 
-    CompletionSet * CompletionSet::shallowCopy() {
-      CompletionSet * copy = new CompletionSet();
+    CompletionSet * CompletionSet::shallowCopy() const {
+        CompletionSet * copy = new CompletionSet();
         for (size_t ic = 0; ic < m_completions.size(); ic++) {
             CompletionConstPtr completion = m_completions[ic];
             copy->m_completions.push_back( completion );
@@ -64,5 +64,5 @@ namespace Opm {
         return copy;
     }
 
-
+    
 }
diff --git a/opm/parser/eclipse/EclipseState/Schedule/CompletionSet.hpp b/opm/parser/eclipse/EclipseState/Schedule/CompletionSet.hpp
index b68135827..58a34748c 100644
--- a/opm/parser/eclipse/EclipseState/Schedule/CompletionSet.hpp
+++ b/opm/parser/eclipse/EclipseState/Schedule/CompletionSet.hpp
@@ -26,7 +26,7 @@
 #include <opm/parser/eclipse/Deck/DeckKeyword.hpp>
 #include <opm/parser/eclipse/Deck/DeckRecord.hpp>
 #include <opm/parser/eclipse/EclipseState/Schedule/ScheduleEnums.hpp>
-
+#include <opm/parser/eclipse/EclipseState/Schedule/Completion.hpp>
 
 namespace Opm {
 
@@ -35,7 +35,7 @@ namespace Opm {
         CompletionSet();
         void add(CompletionConstPtr completion);
         size_t size() const;
-        CompletionSet * shallowCopy();
+        CompletionSet * shallowCopy() const;
         CompletionConstPtr get(size_t index) const;
     private:
         std::vector<CompletionConstPtr> m_completions;