diff --git a/ebos/eclmpiserializer.hh b/ebos/eclmpiserializer.hh
index 2d5b30eb8..03a8a858c 100644
--- a/ebos/eclmpiserializer.hh
+++ b/ebos/eclmpiserializer.hh
@@ -89,7 +89,9 @@ public:
         } else if constexpr (is_variant<T>::value) {
             variant(data);
         } else if constexpr (is_optional<T>::value) {
-          optional(data);
+            optional(data);
+        } else if constexpr (is_map<T>::value) {
+            map(const_cast<T&>(data));
         } else {
           if (m_op == Operation::PACKSIZE)
               m_packSize += Mpi::packSize(data, m_comm);
@@ -243,11 +245,11 @@ public:
         auto handle = [&](auto& d)
         {
             if constexpr (is_vector<Data>::value)
-                this->vector(d);
+                vector(d);
             else if constexpr (is_ptr<Data>::value)
-                this->ptr(d);
+                ptr(d);
             else if constexpr (is_map<Data>::value)
-                this->map(d);
+                map(d);
             else if constexpr (has_serializeOp<Data>::value)
                 d.serializeOp(*this);
             else
diff --git a/opm/simulators/utils/MPIPacker.cpp b/opm/simulators/utils/MPIPacker.cpp
index c138ed9a8..a596b2132 100644
--- a/opm/simulators/utils/MPIPacker.cpp
+++ b/opm/simulators/utils/MPIPacker.cpp
@@ -27,7 +27,6 @@
 #if HAVE_MPI
 #include <ebos/eclmpiserializer.hh>
 #endif
-#include <opm/input/eclipse/EclipseState/Util/OrderedMap.hpp>
 
 namespace Opm
 {
@@ -154,28 +153,6 @@ std::size_t packSize(const std::string& str, Opm::Parallel::MPIComm comm)
     return packSize(str.c_str(), comm);
 }
 
-template<class T1, class T2, class C, class A>
-std::size_t packSize(const std::map<T1,T2,C,A>& data, Opm::Parallel::MPIComm comm)
-{
-    std::size_t totalSize = packSize(data.size(), comm);
-    for (const auto& entry: data)
-    {
-        totalSize += packSize(entry, comm);
-    }
-    return totalSize;
-}
-
-template<class T1, class T2, class H, class P, class A>
-std::size_t packSize(const std::unordered_map<T1,T2,H,P,A>& data, Opm::Parallel::MPIComm comm)
-{
-    std::size_t totalSize = packSize(data.size(), comm);
-    for (const auto& entry: data)
-    {
-        totalSize += packSize(entry, comm);
-    }
-    return totalSize;
-}
-
 template<class T, std::size_t N>
 std::size_t packSize(const std::array<T,N>& data, Opm::Parallel::MPIComm comm)
 {
@@ -372,30 +349,6 @@ void pack(const std::string& str, std::vector<char>& buffer, int& position,
     pack(str.c_str(), buffer, position, comm);
 }
 
-template<class T1, class T2, class C, class A>
-void pack(const std::map<T1,T2,C,A>& data, std::vector<char>& buffer, int& position,
-          Opm::Parallel::MPIComm comm)
-{
-    pack(data.size(), buffer, position, comm);
-
-    for (const auto& entry: data)
-    {
-        pack(entry, buffer, position, comm);
-    }
-}
-
-template<class T1, class T2, class H, class P, class A>
-void pack(const std::unordered_map<T1,T2,H,P,A>& data, std::vector<char>& buffer, int& position,
-          Opm::Parallel::MPIComm comm)
-{
-    pack(data.size(), buffer, position, comm);
-
-    for (const auto& entry: data)
-    {
-        pack(entry, buffer, position, comm);
-    }
-}
-
 template<std::size_t Size>
 void pack(const std::bitset<Size>& data, std::vector<char>& buffer,
           int& position, Opm::Parallel::MPIComm comm)
@@ -572,36 +525,6 @@ void unpack(std::string& str, std::vector<char>& buffer, int& position,
     str.append(cStr.data());
 }
 
-template<class T1, class T2, class C, class A>
-void unpack(std::map<T1,T2,C,A>& data, std::vector<char>& buffer, int& position,
-            Opm::Parallel::MPIComm comm)
-{
-    std::size_t size=0;
-    unpack(size, buffer, position, comm);
-
-    for (;size>0; size--)
-    {
-        std::pair<T1,T2> entry;
-        unpack(entry, buffer, position, comm);
-        data.insert(entry);
-    }
-}
-
-template<class T1, class T2, class H, class P, class A>
-void unpack(std::unordered_map<T1,T2,H,P,A>& data, std::vector<char>& buffer, int& position,
-            Opm::Parallel::MPIComm comm)
-{
-    std::size_t size=0;
-    unpack(size, buffer, position, comm);
-
-    for (;size>0; size--)
-    {
-        std::pair<T1,T2> entry;
-        unpack(entry, buffer, position, comm);
-        data.insert(entry);
-    }
-}
-
 template<std::size_t Size>
 void unpack(std::bitset<Size>& data, std::vector<char>& buffer, int& position,
             Opm::Parallel::MPIComm comm)
@@ -643,7 +566,6 @@ INSTANTIATE_PACK_VECTOR(unsigned long long int)
 INSTANTIATE_PACK_VECTOR(std::time_t)
 INSTANTIATE_PACK_VECTOR(std::array<double, 3>)
 INSTANTIATE_PACK_VECTOR(std::pair<bool,double>)
-INSTANTIATE_PACK_VECTOR(std::map<std::string,int>)
 INSTANTIATE_PACK_VECTOR(std::pair<std::string,std::vector<size_t>>)
 INSTANTIATE_PACK_VECTOR(std::pair<int,std::vector<int>>)
 INSTANTIATE_PACK_VECTOR(std::pair<int,std::vector<size_t>>)
@@ -676,17 +598,7 @@ INSTANTIATE_PACK(std::array<bool,3>)
 INSTANTIATE_PACK(std::array<int,3>)
 INSTANTIATE_PACK(std::array<double,4>)
 INSTANTIATE_PACK(std::array<double,5>)
-INSTANTIATE_PACK(std::map<std::pair<int,int>,std::pair<bool,double>>)
 INSTANTIATE_PACK(std::pair<double, double>)
-INSTANTIATE_PACK(std::map<std::string,std::vector<int>>)
-INSTANTIATE_PACK(std::map<std::string,std::map<std::pair<int,int>,int>>)
-INSTANTIATE_PACK(std::map<std::string,int>)
-INSTANTIATE_PACK(std::map<std::string,double>)
-INSTANTIATE_PACK(std::map<int,int>)
-INSTANTIATE_PACK(std::unordered_map<std::string,size_t>)
-INSTANTIATE_PACK(std::unordered_map<std::string,size_t,Opm::OrderedMapDetail::TruncatedStringHash<std::string::npos>, Opm::OrderedMapDetail::TruncatedStringEquals<std::string::npos>>)
-INSTANTIATE_PACK(std::unordered_map<std::string,size_t,Opm::OrderedMapDetail::TruncatedStringHash<8>, Opm::OrderedMapDetail::TruncatedStringEquals<8>>)
-INSTANTIATE_PACK(std::unordered_map<std::string,std::string>)
 INSTANTIATE_PACK(std::unordered_set<std::string>)
 INSTANTIATE_PACK(std::set<std::string>)
 INSTANTIATE_PACK(std::bitset<4>)
diff --git a/opm/simulators/utils/MPIPacker.hpp b/opm/simulators/utils/MPIPacker.hpp
index 03ffefe89..4f2570d13 100644
--- a/opm/simulators/utils/MPIPacker.hpp
+++ b/opm/simulators/utils/MPIPacker.hpp
@@ -26,12 +26,10 @@
 
 #include <bitset>
 #include <cstddef>
-#include <map>
 #include <set>
 #include <string>
 #include <tuple>
 #include <typeinfo>
-#include <unordered_map>
 #include <unordered_set>
 #include <vector>
 
@@ -104,12 +102,6 @@ std::size_t packSize(const std::array<T,N>& data, Opm::Parallel::MPIComm comm);
 
 std::size_t packSize(const char* str, Opm::Parallel::MPIComm comm);
 
-template<class T1, class T2, class C, class A>
-std::size_t packSize(const std::map<T1,T2,C,A>& data, Opm::Parallel::MPIComm comm);
-
-template<class T1, class T2, class H, class P, class A>
-std::size_t packSize(const std::unordered_map<T1,T2,H,P,A>& data, Opm::Parallel::MPIComm comm);
-
 template<std::size_t Size>
 std::size_t packSize(const std::bitset<Size>& data, Opm::Parallel::MPIComm comm);
 
@@ -186,14 +178,6 @@ template<class T, size_t N>
 void pack(const std::array<T,N>& data, std::vector<char>& buffer, int& position,
           Opm::Parallel::MPIComm comm);
 
-template<class T1, class T2, class C, class A>
-void pack(const std::map<T1,T2,C,A>& data, std::vector<char>& buffer, int& position,
-          Opm::Parallel::MPIComm comm);
-
-template<class T1, class T2, class H, class P, class A>
-void pack(const std::unordered_map<T1,T2,H,P,A>& data, std::vector<char>& buffer, int& position,
-          Opm::Parallel::MPIComm comm);
-
 void pack(const char* str, std::vector<char>& buffer, int& position,
           Opm::Parallel::MPIComm comm);
 
@@ -275,14 +259,6 @@ template<class T, size_t N>
 void unpack(std::array<T,N>& data, std::vector<char>& buffer, int& position,
           Opm::Parallel::MPIComm comm);
 
-template<class T1, class T2, class C, class A>
-void unpack(std::map<T1,T2,C,A>& data, std::vector<char>& buffer, int& position,
-            Opm::Parallel::MPIComm comm);
-
-template<class T1, class T2, class H, class P, class A>
-void unpack(std::unordered_map<T1,T2,H,P,A>& data, std::vector<char>& buffer, int& position,
-            Opm::Parallel::MPIComm comm);
-
 void unpack(char* str, std::size_t length, std::vector<char>& buffer, int& position,
             Opm::Parallel::MPIComm comm);