diff --git a/src/one-body-sample.cc b/src/one-body-sample.cc
index 145a8e1e77492d2ba00df96ee1789593e497e39f..e91cb77891d3e3b86db62f6789a3c4b09969f10c 100644
--- a/src/one-body-sample.cc
+++ b/src/one-body-sample.cc
@@ -180,8 +180,8 @@ int main() {
     u1 = 0;
     VectorType u2 = u1;
 
+    VectorType f(grid.size(grid.maxLevel(), dim));
     for (size_t run = 1; run <= runs; ++run) {
-      VectorType f(grid.size(grid.maxLevel(), dim));
       f = 0;
       VectorType neumannTerm(grid.size(grid.maxLevel(), dim));
       assemble_neumann<GridType, GridType::LeafGridView, SmallVector, P1Basis>(