diff --git a/dumux/material/fluidmatrixinteractions/porenetwork/pore/2p/localrulesforplatonicbody.hh b/dumux/material/fluidmatrixinteractions/porenetwork/pore/2p/localrulesforplatonicbody.hh
index c97b28fcc132065e4704ec0b226b47a7aa272033..b5d011dc597d55efae76da007ad9768bc3d5c07d 100644
--- a/dumux/material/fluidmatrixinteractions/porenetwork/pore/2p/localrulesforplatonicbody.hh
+++ b/dumux/material/fluidmatrixinteractions/porenetwork/pore/2p/localrulesforplatonicbody.hh
@@ -28,6 +28,7 @@
 #include <algorithm>
 #include <cassert>
 #include <cmath>
+#include <optional>
 #include <dune/common/math.hh>
 #include <dumux/common/optionalscalar.hh>
 #include <dumux/common/spline.hh>