diff --git a/avogadro/qtplugins/forcefield/forcefield.cpp b/avogadro/qtplugins/forcefield/forcefield.cpp
index 85a0b426b5..d7fe113b7e 100644
--- a/avogadro/qtplugins/forcefield/forcefield.cpp
+++ b/avogadro/qtplugins/forcefield/forcefield.cpp
@@ -230,13 +230,11 @@ void Forcefield::setupMethod()
     m_methodName = recommendedForceField();
   }
 
-  if (m_method == nullptr) {
-    // we have to create the calculator
-    m_method = Calc::EnergyManager::instance().model(m_methodName);
-  } else if (m_method->identifier() != m_methodName) {
+  if (m_method != nullptr) {
     delete m_method; // delete the previous one
-    m_method = Calc::EnergyManager::instance().model(m_methodName);
   }
+  m_method = Calc::EnergyManager::instance().model(m_methodName);
+
   if (m_method != nullptr)
     m_method->setMolecule(m_molecule);
 }
diff --git a/avogadro/qtplugins/forcefield/obenergy.cpp b/avogadro/qtplugins/forcefield/obenergy.cpp
index 9ca9f7cec6..332698b9d0 100644
--- a/avogadro/qtplugins/forcefield/obenergy.cpp
+++ b/avogadro/qtplugins/forcefield/obenergy.cpp
@@ -35,8 +35,8 @@ class OBEnergy::Private
 
   ~Private()
   {
-    delete m_obmol;
-    delete m_forceField;
+    if (m_obmol != nullptr)
+      delete m_obmol;
   }
 };
 
diff --git a/avogadro/qtplugins/forcefield/obmmenergy.cpp b/avogadro/qtplugins/forcefield/obmmenergy.cpp
index 49c67194be..8a7e9a3c0b 100644
--- a/avogadro/qtplugins/forcefield/obmmenergy.cpp
+++ b/avogadro/qtplugins/forcefield/obmmenergy.cpp
@@ -70,7 +70,8 @@ OBMMEnergy::OBMMEnergy(const std::string& method)
 OBMMEnergy::~OBMMEnergy()
 {
   delete m_inputFormat;
-  delete m_process;
+  if (m_process != nullptr)
+    delete m_process;
 }
 
 bool OBMMEnergy::acceptsRadicals() const