diff --git a/opm/parser/eclipse/Units/UnitSystem.hpp b/opm/parser/eclipse/Units/UnitSystem.hpp
index 8bd7395e7..6e3806edf 100644
--- a/opm/parser/eclipse/Units/UnitSystem.hpp
+++ b/opm/parser/eclipse/Units/UnitSystem.hpp
@@ -66,7 +66,7 @@ namespace Opm {
             water_inverse_formation_volume_factor,
         };
 
-        UnitSystem(UnitType unit = UnitType::UNIT_TYPE_METRIC);
+        explicit UnitSystem(UnitType unit = UnitType::UNIT_TYPE_METRIC);
 
         const std::string& getName() const;
         UnitType getType() const;
diff --git a/opm/parser/eclipse/Units/tests/UnitTests.cpp b/opm/parser/eclipse/Units/tests/UnitTests.cpp
index 167ca6b9b..826dc7cb0 100644
--- a/opm/parser/eclipse/Units/tests/UnitTests.cpp
+++ b/opm/parser/eclipse/Units/tests/UnitTests.cpp
@@ -174,7 +174,7 @@ BOOST_AUTO_TEST_CASE(DimensionEqual) {
 
 namespace Opm {
 inline std::ostream& operator<<( std::ostream& stream, const UnitSystem& us ) {
-    return stream << us.getName() << " :: " << us.getType();
+    return stream << us.getName() << " :: " << static_cast<int>(us.getType());
 }
 }