diff --git a/src/one-body-sample.cc b/src/one-body-sample.cc
index ef3a3c2945a97f4f324d1765997c2b26d0bd41b1..0a679e5dd4c7b9436d4a1c62d6a2537fefa0f942 100644
--- a/src/one-body-sample.cc
+++ b/src/one-body-sample.cc
@@ -192,7 +192,7 @@ int main(int argc, char *argv[]) {
         parset.get<size_t>("solver.maxiterations");
     auto const solver_tolerance = parset.get<double>("solver.tolerance");
 
-    auto const levels = parset.get<int>("grid.refinements") + 1;
+    auto const levels = parset.get<size_t>("grid.refinements") + 1;
 
     auto const verbose = parset.get<bool>("verbose");
     Solver::VerbosityMode verbosity = verbose ? Solver::FULL : Solver::QUIET;