diff --git a/src/plugins/solverinterface.cpp b/src/plugins/solverinterface.cpp
index 5923ffd13a..5a7b57dfe1 100644
--- a/src/plugins/solverinterface.cpp
+++ b/src/plugins/solverinterface.cpp
@@ -25,10 +25,6 @@ along with this program. If not, see <https://gnu.org/licenses>.
 
 //==============================================================================
 
-#include <QCoreApplication>
-
-//==============================================================================
-
 void doNonLinearSolve(char *pRuntime,
                       void (*pFunction)(double *, double *, void *),
                       double *pParameters, int pSize, void *pUserData)
@@ -135,32 +131,33 @@ NlaSolver::~NlaSolver() = default;
 
 //==============================================================================
 
-NlaSolver * nlaSolver(const QString &pRuntimeAddress)
+QString objectAddress(QObject *pObject)
 {
-    // Return the runtime's NLA solver
-
-    QVariant res = qApp->property(pRuntimeAddress.toUtf8().constData());
+    // Return the given object's address as a string
 
-    return res.isValid()?reinterpret_cast<NlaSolver *>(res.toULongLong()):nullptr;
+    return QString::number(quint64(pObject));
 }
 
 //==============================================================================
 
-void setNlaSolver(const QString &pRuntimeAddress, NlaSolver *pGlobalNlaSolver)
+NlaSolver * nlaSolver(const QString &pObjectAddress)
 {
-    // Keep track of the runtime's NLA solver
+    // Return the runtime's NLA solver
+
+    QObject *object = reinterpret_cast<NlaSolver *>(QVariant(pObjectAddress).toULongLong());
+    QVariant res = object->property(pObjectAddress.toUtf8().constData());
 
-    qApp->setProperty(pRuntimeAddress.toUtf8().constData(),
-                      quint64(pGlobalNlaSolver));
+    return res.isValid()?reinterpret_cast<NlaSolver *>(res.toULongLong()):nullptr;
 }
 
 //==============================================================================
 
-void unsetNlaSolver(const QString &pRuntimeAddress)
+void setNlaSolver(QObject *pObject, NlaSolver *pGlobalNlaSolver)
 {
-    // Stop tracking the runtime's NLA solver
+    // Keep track of the runtime's NLA solver
 
-    qApp->setProperty(pRuntimeAddress.toUtf8().constData(), QVariant::Invalid);
+    pObject->setProperty(objectAddress(pObject).toUtf8().constData(),
+                         quint64(pGlobalNlaSolver));
 }
 
 //==============================================================================
diff --git a/src/plugins/solverinterface.h b/src/plugins/solverinterface.h
index 38eef5661d..43d1cfbe58 100644
--- a/src/plugins/solverinterface.h
+++ b/src/plugins/solverinterface.h
@@ -111,10 +111,11 @@ class NlaSolver : public Solver
 
 //==============================================================================
 
-NlaSolver * nlaSolver(const QString &pRuntimeAddress);
+QString objectAddress(QObject *pObject);
 
-void setNlaSolver(const QString &pRuntimeAddress, NlaSolver *pGlobalNlaSolver);
-void unsetNlaSolver(const QString &pRuntimeAddress);
+NlaSolver * nlaSolver(const QString &pObjectAddress);
+
+void setNlaSolver(QObject *pObject, NlaSolver *pGlobalNlaSolver);
 
 //==============================================================================
 
diff --git a/src/plugins/support/CellMLSupport/src/cellmlfileruntime.cpp b/src/plugins/support/CellMLSupport/src/cellmlfileruntime.cpp
index a3419b05e3..45d88872c2 100644
--- a/src/plugins/support/CellMLSupport/src/cellmlfileruntime.cpp
+++ b/src/plugins/support/CellMLSupport/src/cellmlfileruntime.cpp
@@ -585,15 +585,6 @@ void CellmlFileRuntime::update(CellmlFile *pCellmlFile, bool pAll)
 
 //==============================================================================
 
-QString CellmlFileRuntime::address() const
-{
-    // Return our address as a string
-
-    return QString::number(quint64(this));
-}
-
-//==============================================================================
-
 bool CellmlFileRuntime::isValid() const
 {
     // The runtime is valid if no issues were found
@@ -969,7 +960,7 @@ QString CellmlFileRuntime::cleanCode(const std::wstring &pCode)
     // new parameter to all our calls to doNonLinearSolve() so that
     // doNonLinearSolve() can retrieve the correct instance of our NLA solver
 
-    res.replace("do_nonlinearsolve(", QString(R"(doNonLinearSolve("%1", )").arg(address()));
+    res.replace("do_nonlinearsolve(", QString(R"(doNonLinearSolve("%1", )").arg(Solver::objectAddress(this)));
 
     return res;
 }
diff --git a/src/plugins/support/CellMLSupport/src/cellmlfileruntime.h b/src/plugins/support/CellMLSupport/src/cellmlfileruntime.h
index 0f6d8931b8..2bb37a2b83 100644
--- a/src/plugins/support/CellMLSupport/src/cellmlfileruntime.h
+++ b/src/plugins/support/CellMLSupport/src/cellmlfileruntime.h
@@ -140,8 +140,6 @@ class CELLMLSUPPORT_EXPORT CellmlFileRuntime : public QObject
 
     void update(CellmlFile *pCellmlFile, bool pAll = true);
 
-    QString address() const;
-
     bool isValid() const;
 
     bool needNlaSolver() const;
diff --git a/src/plugins/support/SimulationSupport/src/simulation.cpp b/src/plugins/support/SimulationSupport/src/simulation.cpp
index 17fe5dd197..17d6794cb3 100644
--- a/src/plugins/support/SimulationSupport/src/simulation.cpp
+++ b/src/plugins/support/SimulationSupport/src/simulation.cpp
@@ -531,11 +531,10 @@ void SimulationData::reset(bool pInitialize, bool pAll)
 
     if (runtime->needNlaSolver()) {
         // Set our NLA solver
-        // Note: we unset it at the end of this method...
 
         nlaSolver = static_cast<Solver::NlaSolver *>(nlaSolverInterface()->solverInstance());
 
-        Solver::setNlaSolver(runtime->address(), nlaSolver);
+        Solver::setNlaSolver(runtime, nlaSolver);
 
         // Keep track of any error that might be reported by our NLA solver
 
@@ -595,8 +594,6 @@ void SimulationData::reset(bool pInitialize, bool pAll)
 
     if (nlaSolver != nullptr) {
         delete nlaSolver;
-
-        Solver::unsetNlaSolver(runtime->address());
     }
 
     // Let people know whether our data is clean, i.e. not modified, and ask our
diff --git a/src/plugins/support/SimulationSupport/src/simulationworker.cpp b/src/plugins/support/SimulationSupport/src/simulationworker.cpp
index 5da0dd3b68..328d82f70e 100644
--- a/src/plugins/support/SimulationSupport/src/simulationworker.cpp
+++ b/src/plugins/support/SimulationSupport/src/simulationworker.cpp
@@ -90,14 +90,13 @@ void SimulationWorker::run()
     auto odeSolver = static_cast<Solver::OdeSolver *>(mSimulation->data()->odeSolverInterface()->solverInstance());
 
     // Set up our NLA solver, if needed
-    // Note: we unset it at the end of this method...
 
     Solver::NlaSolver *nlaSolver = nullptr;
 
     if (mRuntime->needNlaSolver()) {
         nlaSolver = static_cast<Solver::NlaSolver *>(mSimulation->data()->nlaSolverInterface()->solverInstance());
 
-        Solver::setNlaSolver(mRuntime->address(), nlaSolver);
+        Solver::setNlaSolver(mRuntime, nlaSolver);
     }
 
     // Keep track of any error that might be reported by any of our solvers
@@ -254,8 +253,6 @@ void SimulationWorker::run()
 
     if (nlaSolver != nullptr) {
         delete nlaSolver;
-
-        Solver::unsetNlaSolver(mRuntime->address());
     }
 
     // Reset our simulation owner's knowledge of us