diff --git a/avogadro/qtplugins/forcefield/obenergy.cpp b/avogadro/qtplugins/forcefield/obenergy.cpp
index 03cf1d6dd4..9ca9f7cec6 100644
--- a/avogadro/qtplugins/forcefield/obenergy.cpp
+++ b/avogadro/qtplugins/forcefield/obenergy.cpp
@@ -137,6 +137,14 @@ OBEnergy::OBEnergy(const std::string& method)
 
 OBEnergy::~OBEnergy() {}
 
+bool OBEnergy::acceptsRadicals() const
+{
+  if (m_identifier == "UFF")
+    return true;
+
+  return false;
+}
+
 Calc::EnergyCalculator* OBEnergy::newInstance() const
 {
   return new OBEnergy(m_name);
diff --git a/avogadro/qtplugins/forcefield/obenergy.h b/avogadro/qtplugins/forcefield/obenergy.h
index c9a605dce8..2ff37b9a9e 100644
--- a/avogadro/qtplugins/forcefield/obenergy.h
+++ b/avogadro/qtplugins/forcefield/obenergy.h
@@ -48,6 +48,10 @@ class OBEnergy : public Avogadro::Calc::EnergyCalculator
   // gradient (which may be unsupported and fall back to numeric)
   void gradient(const Eigen::VectorXd& x, Eigen::VectorXd& grad) override;
 
+  bool acceptsIons() const override { return true; }
+  // UFF can handle radicals
+  bool acceptsRadicals() const override;
+
 private:
   class Private;
 
diff --git a/avogadro/qtplugins/forcefield/obmmenergy.cpp b/avogadro/qtplugins/forcefield/obmmenergy.cpp
index 41bae1977f..49c67194be 100644
--- a/avogadro/qtplugins/forcefield/obmmenergy.cpp
+++ b/avogadro/qtplugins/forcefield/obmmenergy.cpp
@@ -73,6 +73,15 @@ OBMMEnergy::~OBMMEnergy()
   delete m_process;
 }
 
+bool OBMMEnergy::acceptsRadicals() const
+{
+  // UFF will figure something out
+  if (m_identifier == "UFF")
+    return true;
+
+  return false;
+}
+
 QByteArray OBMMEnergy::writeAndRead(const QByteArray& input)
 {
   if (m_process == nullptr)
diff --git a/avogadro/qtplugins/forcefield/obmmenergy.h b/avogadro/qtplugins/forcefield/obmmenergy.h
index 63d0d9d2b3..52a21ebfb6 100644
--- a/avogadro/qtplugins/forcefield/obmmenergy.h
+++ b/avogadro/qtplugins/forcefield/obmmenergy.h
@@ -66,6 +66,10 @@ class OBMMEnergy : public Avogadro::Calc::EnergyCalculator
   // gradient (which may be unsupported and fall back to numeric)
   void gradient(const Eigen::VectorXd& x, Eigen::VectorXd& grad) override;
 
+  bool acceptsIons() const override { return true; }
+  // UFF can handle radicals
+  bool acceptsRadicals() const override;
+
   /**
    * @brief Synchronous use of the QProcess.
    */