diff --git a/writer/HDF5NXmx.cpp b/writer/HDF5NXmx.cpp
index a570f1db..8728dd16 100644
--- a/writer/HDF5NXmx.cpp
+++ b/writer/HDF5NXmx.cpp
@@ -542,7 +542,7 @@ void NXmx::Metrology(const StartMessage &start) {
                    start.pixel_size_x);
 }
 
-void SaveUnitCell( HDF5Group& group, const std::string& name, const UnitCell& unit_cell,) {
+void SaveUnitCell( HDF5Group& group, const std::string& name, const UnitCell& unit_cell) {
     std::vector<float> v = {unit_cell.a, unit_cell.b, unit_cell.c,
                             unit_cell.alpha, unit_cell.beta, unit_cell.gamma};
     group.SaveVector(name, v);