diff --git a/opm/simulators/linalg/parallelamgbackend.hh b/opm/simulators/linalg/parallelamgbackend.hh
index 262297eac..22178de6a 100644
--- a/opm/simulators/linalg/parallelamgbackend.hh
+++ b/opm/simulators/linalg/parallelamgbackend.hh
@@ -255,6 +255,7 @@ protected:
     }
 #endif
 
+    // trailing return type with decltype used for detecting existence of setUseFixedOrder member function by overloading the setUseFixedOrder function
     template <typename C>
     auto setUseFixedOrder(C criterion, bool booleanValue) -> decltype(criterion.setUseFixedOrder(booleanValue))
     {