diff --git a/src/mesh/ConnectivityBuilderBase.cpp b/src/mesh/ConnectivityBuilderBase.cpp
index c13e6993a2f05f4b4ee1278d51acbb100b2adba8..60c38bfb84fb975c0e2cdc3b07d1d97e39eb0021 100644
--- a/src/mesh/ConnectivityBuilderBase.cpp
+++ b/src/mesh/ConnectivityBuilderBase.cpp
@@ -8,6 +8,7 @@
 #include <utils/PugsMacros.hpp>
 
 #include <map>
+#include <unordered_map>
 #include <vector>
 
 template <size_t Dimension>