diff --git a/exercises/solution/exercise-model/model.hh b/exercises/solution/exercise-model/model.hh
index 2070f2cce64131e05ad89d844de5a939d5ca6b1c..56bd5739f8ef0870484b831f073fb6d9d2d6f539 100644
--- a/exercises/solution/exercise-model/model.hh
+++ b/exercises/solution/exercise-model/model.hh
@@ -23,6 +23,7 @@
 // In the file `model.hh`, we define the volume variables, the model equations, and
 // set all default model properties.
 
+#include <dune/common/fvector.hh>
 #include <dumux/common/math.hh>
 #include <dumux/common/properties.hh>
 #include <dumux/common/numeqvector.hh>