diff --git a/avogadro/calc/lennardjones.h b/avogadro/calc/lennardjones.h
index ca31279113..821b6827a4 100644
--- a/avogadro/calc/lennardjones.h
+++ b/avogadro/calc/lennardjones.h
@@ -35,6 +35,8 @@ class AVOGADROCALC_EXPORT LennardJones : public EnergyCalculator
     return "Universal Lennard-Jones potential";
   }
 
+  bool acceptsIons() const override { return true; }
+  bool acceptsRadicals() const override { return true; }
   bool acceptsUnitCell() const override { return true; }
 
   Core::Molecule::ElementMask elements() const override { return (m_elements); }