diff --git a/opm/parser/eclipse/EclipseState/Schedule/Schedule.hpp b/opm/parser/eclipse/EclipseState/Schedule/Schedule.hpp
index 9ede36bb4..5d0517d3c 100644
--- a/opm/parser/eclipse/EclipseState/Schedule/Schedule.hpp
+++ b/opm/parser/eclipse/EclipseState/Schedule/Schedule.hpp
@@ -118,7 +118,7 @@ namespace Opm
         using VFPInjMap = std::map<int, DynamicState<std::shared_ptr<VFPInjTable>>>;
 
         Schedule() = default;
-        Schedule(std::shared_ptr<const Python>) {}
+        explicit Schedule(std::shared_ptr<const Python>) {}
         Schedule(const Deck& deck,
                  const EclipseGrid& grid,
                  const FieldPropsManager& fp,