diff --git a/opm/simulators/utils/ParallelRestart.cpp b/opm/simulators/utils/ParallelRestart.cpp
index b304e3051..66a83c401 100644
--- a/opm/simulators/utils/ParallelRestart.cpp
+++ b/opm/simulators/utils/ParallelRestart.cpp
@@ -255,33 +255,6 @@ std::size_t packSize(const T* data, std::size_t l, Dune::MPIHelper::MPICommunica
     return packSize(data, l, comm, typename std::is_pod<T>::type());
 }
 
-template<class T>
-std::size_t packSize(const T&, Dune::MPIHelper::MPICommunicator,
-                     std::integral_constant<bool, false>)
-{
-    OPM_THROW(std::logic_error, "Packing not (yet) supported for this non-pod type.");
-}
-
-template<class T>
-std::size_t packSize(const T&, Dune::MPIHelper::MPICommunicator comm,
-                     std::integral_constant<bool, true>)
-{
-#if HAVE_MPI
-    int size{};
-    MPI_Pack_size(1, Dune::MPITraits<T>::getType(), comm, &size);
-    return size;
-#else
-    (void) comm;
-    return 0;
-#endif
-}
-
-template<class T>
-std::size_t packSize(const T& data, Dune::MPIHelper::MPICommunicator comm)
-{
-    return packSize(data, comm, typename std::is_pod<T>::type());
-}
-
 template<class T1, class T2>
 std::size_t packSize(const std::pair<T1,T2>& data, Dune::MPIHelper::MPICommunicator comm)
 {
@@ -1862,35 +1835,6 @@ void pack(const T* data, std::size_t l, std::vector<char>& buffer, int& position
     pack(data, l, buffer, position, comm, typename std::is_pod<T>::type());
 }
 
-template<class T>
-void pack(const T&, std::vector<char>&, int&,
-          Dune::MPIHelper::MPICommunicator, std::integral_constant<bool, false>)
-{
-    OPM_THROW(std::logic_error, "Packing not (yet) supported for this non-pod type.");
-}
-
-template<class T>
-void pack(const T& data, std::vector<char>& buffer, int& position,
-          Dune::MPIHelper::MPICommunicator comm, std::integral_constant<bool, true>)
-{
-#if HAVE_MPI
-    MPI_Pack(&data, 1, Dune::MPITraits<T>::getType(), buffer.data(),
-             buffer.size(), &position, comm);
-#else
-    (void) data;
-    (void) comm;
-    (void) buffer;
-    (void) position;
-#endif
-}
-
-template<class T>
-void pack(const T& data, std::vector<char>& buffer, int& position,
-          Dune::MPIHelper::MPICommunicator comm)
-{
-    pack(data, buffer, position, comm, typename std::is_pod<T>::type());
-}
-
 template<class T1, class T2>
 void pack(const std::pair<T1,T2>& data, std::vector<char>& buffer, int& position,
           Dune::MPIHelper::MPICommunicator comm)
@@ -3555,35 +3499,6 @@ void unpack(T* data, const std::size_t& l, std::vector<char>& buffer, int& posit
     unpack(data, l, buffer, position, comm, typename std::is_pod<T>::type());
 }
 
-template<class T>
-void unpack(T&, std::vector<char>&, int&,
-            Dune::MPIHelper::MPICommunicator, std::integral_constant<bool, false>)
-{
-    OPM_THROW(std::logic_error, "Packing not (yet) supported for this non-pod type.");
-}
-
-template<class T>
-void unpack(T& data, std::vector<char>& buffer, int& position,
-            Dune::MPIHelper::MPICommunicator comm, std::integral_constant<bool, true>)
-{
-#if HAVE_MPI
-    MPI_Unpack(buffer.data(), buffer.size(), &position, &data, 1,
-               Dune::MPITraits<T>::getType(), comm);
-#else
-    (void) data;
-    (void) comm;
-    (void) buffer;
-    (void) position;
-#endif
-}
-
-template<class T>
-void unpack(T& data, std::vector<char>& buffer, int& position,
-            Dune::MPIHelper::MPICommunicator comm)
-{
-    unpack(data, buffer, position, comm, typename std::is_pod<T>::type());
-}
-
 template<class T1, class T2>
 void unpack(std::pair<T1,T2>& data, std::vector<char>& buffer, int& position,
             Dune::MPIHelper::MPICommunicator comm)
diff --git a/opm/simulators/utils/ParallelRestart.hpp b/opm/simulators/utils/ParallelRestart.hpp
index 22a459bb2..2e13fe793 100644
--- a/opm/simulators/utils/ParallelRestart.hpp
+++ b/opm/simulators/utils/ParallelRestart.hpp
@@ -193,14 +193,30 @@ std::size_t packSize(const T* data, std::size_t l, Dune::MPIHelper::MPICommunica
 
 template<class T>
 std::size_t packSize(const T&, Dune::MPIHelper::MPICommunicator,
-                     std::integral_constant<bool, false>);
+                     std::integral_constant<bool, false>)
+{
+    OPM_THROW(std::logic_error, "Packing not (yet) supported for this non-pod type.");
+}
 
 template<class T>
 std::size_t packSize(const T&, Dune::MPIHelper::MPICommunicator comm,
-                     std::integral_constant<bool, true>);
+                     std::integral_constant<bool, true>)
+{
+#if HAVE_MPI
+    int size{};
+    MPI_Pack_size(1, Dune::MPITraits<T>::getType(), comm, &size);
+    return size;
+#else
+    (void) comm;
+    return 0;
+#endif
+}
 
 template<class T>
-std::size_t packSize(const T& data, Dune::MPIHelper::MPICommunicator comm);
+std::size_t packSize(const T& data, Dune::MPIHelper::MPICommunicator comm)
+{
+    return packSize(data, comm, typename std::is_pod<T>::type());
+}
 
 template<class T1, class T2>
 std::size_t packSize(const std::pair<T1,T2>& data, Dune::MPIHelper::MPICommunicator comm);
@@ -271,16 +287,32 @@ void pack(const T* data, std::size_t l, std::vector<char>& buffer, int& position
 
 template<class T>
 void pack(const T&, std::vector<char>&, int&,
-          Dune::MPIHelper::MPICommunicator, std::integral_constant<bool, false>);
+          Dune::MPIHelper::MPICommunicator, std::integral_constant<bool, false>)
+{
+    OPM_THROW(std::logic_error, "Packing not (yet) supported for this non-pod type.");
+}
 
 template<class T>
 void pack(const T& data, std::vector<char>& buffer, int& position,
-          Dune::MPIHelper::MPICommunicator comm, std::integral_constant<bool, true>);
-
+          Dune::MPIHelper::MPICommunicator comm, std::integral_constant<bool, true>)
+{
+#if HAVE_MPI
+    MPI_Pack(&data, 1, Dune::MPITraits<T>::getType(), buffer.data(),
+             buffer.size(), &position, comm);
+#else
+    (void) data;
+    (void) comm;
+    (void) buffer;
+    (void) position;
+#endif
+}
 
 template<class T>
 void pack(const T& data, std::vector<char>& buffer, int& position,
-          Dune::MPIHelper::MPICommunicator comm);
+          Dune::MPIHelper::MPICommunicator comm)
+{
+    pack(data, buffer, position, comm, typename std::is_pod<T>::type());
+}
 
 template<class T1, class T2>
 void pack(const std::pair<T1,T2>& data, std::vector<char>& buffer, int& position,
@@ -364,15 +396,32 @@ void unpack(T* data, const std::size_t& l, std::vector<char>& buffer, int& posit
 
 template<class T>
 void unpack(T&, std::vector<char>&, int&,
-            Dune::MPIHelper::MPICommunicator, std::integral_constant<bool, false>);
+            Dune::MPIHelper::MPICommunicator, std::integral_constant<bool, false>)
+{
+    OPM_THROW(std::logic_error, "Packing not (yet) supported for this non-pod type.");
+}
 
 template<class T>
 void unpack(T& data, std::vector<char>& buffer, int& position,
-            Dune::MPIHelper::MPICommunicator comm, std::integral_constant<bool, true>);
+            Dune::MPIHelper::MPICommunicator comm, std::integral_constant<bool, true>)
+{
+#if HAVE_MPI
+    MPI_Unpack(buffer.data(), buffer.size(), &position, &data, 1,
+               Dune::MPITraits<T>::getType(), comm);
+#else
+    (void) data;
+    (void) comm;
+    (void) buffer;
+    (void) position;
+#endif
+}
 
 template<class T>
 void unpack(T& data, std::vector<char>& buffer, int& position,
-            Dune::MPIHelper::MPICommunicator comm);
+            Dune::MPIHelper::MPICommunicator comm)
+{
+    unpack(data, buffer, position, comm, typename std::is_pod<T>::type());
+}
 
 template<class T1, class T2>
 void unpack(std::pair<T1,T2>& data, std::vector<char>& buffer, int& position,