Make the constructor explicit

diff --git a/include/deal.II/lac/petsc_precondition.h b/include/deal.II/lac/petsc_precondition.h
index 16df0d8039f66d777e2cb13f35b5f79a6b1b30e3..010d2fc750b6b8ec939904159987ed6c9c32040a 100644 (file)
--- a/include/deal.II/lac/petsc_precondition.h
+++ b/include/deal.II/lac/petsc_precondition.h
@@ -62,7 +62,7 @@ namespace PETScWrappers
     /**
      * Constructor.
      */
-    PreconditionBase(const MPI_Comm &mpi_communicator = MPI_COMM_NULL);
+    explicit PreconditionBase(const MPI_Comm &mpi_communicator = MPI_COMM_NULL);
 
     /**
      * Destructor.