add missing DEAL_II_WITH_SLEPC in petsc_solver.h

diff --git a/include/deal.II/lac/petsc_solver.h b/include/deal.II/lac/petsc_solver.h
index 89e7914ff911294ca9c3d52b74aced33f772a6c1..f23a43bf587b983d71a53561b8740caa116aa4a6 100644 (file)
--- a/include/deal.II/lac/petsc_solver.h
+++ b/include/deal.II/lac/petsc_solver.h
@@ -249,10 +249,12 @@ namespace PETScWrappers
      */
     std_cxx11::shared_ptr<SolverData> solver_data;
 
+#ifdef DEAL_II_WITH_SLEPC
     /**
-     * Make the transformation class a friend, since it needs to set the solver.
+     * Make the transformation class a friend, since it needs to set the KSP solver.
      */
-    friend SLEPcWrappers::TransformationBase;
+    friend class SLEPcWrappers::TransformationBase;
+#endif
   };