diff --git a/MaterialPicker.cc b/MaterialPicker.cc
index 1e050bcadb8a9d14f7c3c44b3d165a2abf5763c3..08dcba76042f66cb34b521120e11fa62d781a057 100644
--- a/MaterialPicker.cc
+++ b/MaterialPicker.cc
@@ -269,7 +269,7 @@ void MaterialPicker::slotMouseEvent(QMouseEvent* _event) {
     return;
 
   if (_event->type() == QEvent::MouseButtonPress) {
-    unsigned int node_idx, target_idx;
+    size_t          node_idx, target_idx;
     OpenMesh::Vec3d hitPoint;
 
     // Get picked object's identifier by picking in scenegraph