diff --git a/opm/simulators/utils/ParallelRestart.cpp b/opm/simulators/utils/ParallelRestart.cpp
index dde9e291e..6e61d22ec 100644
--- a/opm/simulators/utils/ParallelRestart.cpp
+++ b/opm/simulators/utils/ParallelRestart.cpp
@@ -5280,6 +5280,7 @@ INSTANTIATE_PACK_VECTOR(std::vector<double>)
 INSTANTIATE_PACK_VECTOR(bool)
 INSTANTIATE_PACK_VECTOR(char)
 INSTANTIATE_PACK_VECTOR(int)
+INSTANTIATE_PACK_VECTOR(size_t)
 INSTANTIATE_PACK_VECTOR(std::array<double, 3>)
 INSTANTIATE_PACK_VECTOR(std::pair<bool,double>)
 INSTANTIATE_PACK_VECTOR(std::shared_ptr<Group>)