diff --git a/src/horizontal/mo_lib_laplace.cpp b/src/horizontal/mo_lib_laplace.cpp
index 32c6e008d35d8ec80ee80fc97c730d2aca735963..8dac99aae73f8ec60b5e9c2bf592dd006574b814 100644
--- a/src/horizontal/mo_lib_laplace.cpp
+++ b/src/horizontal/mo_lib_laplace.cpp
@@ -253,7 +253,11 @@ void nabla2_scalar_avg_lib(const T* psi_c, const int* cell_neighbor_idx, const i
                                         });
                  }
             }//if
-}//switch
+            break; 
+
+        default: 
+            std::cerr << "Unknown value for cell_type: " << cell_type << '\n';
+    }//switch
 }//void