diff --git a/src/qt/bitcoin.cpp b/src/qt/bitcoin.cpp
index 676c15ea43..9bee009017 100644
--- a/src/qt/bitcoin.cpp
+++ b/src/qt/bitcoin.cpp
@@ -281,8 +281,11 @@ void BitcoinApplication::parameterSetup()
     m_node.initParameterInteraction();
 }
 
-void BitcoinApplication::SetPrune(bool prune, bool force) {
-     optionsModel->SetPrune(prune, force);
+void BitcoinApplication::SetPrune(bool prune, bool force)
+{
+    // If prune is set, intentionally override existing prune size with
+    // the default size since this is called when choosing a new datadir.
+    optionsModel->SetPruneTargetGB(prune ? DEFAULT_PRUNE_TARGET_GB : 0, force);
 }
 
 void BitcoinApplication::requestInitialize()
diff --git a/src/qt/optionsmodel.cpp b/src/qt/optionsmodel.cpp
index c721c801e1..1512babbc3 100644
--- a/src/qt/optionsmodel.cpp
+++ b/src/qt/optionsmodel.cpp
@@ -92,7 +92,7 @@ void OptionsModel::Init(bool resetSettings)
         settings.setValue("bPrune", false);
     if (!settings.contains("nPruneSize"))
         settings.setValue("nPruneSize", DEFAULT_PRUNE_TARGET_GB);
-    SetPrune(settings.value("bPrune").toBool());
+    SetPruneEnabled(settings.value("bPrune").toBool());
 
     if (!settings.contains("nDatabaseCache"))
         settings.setValue("nDatabaseCache", (qint64)nDefaultDbCache);
@@ -236,7 +236,7 @@ static const QString GetDefaultProxyAddress()
     return QString("%1:%2").arg(DEFAULT_GUI_PROXY_HOST).arg(DEFAULT_GUI_PROXY_PORT);
 }
 
-void OptionsModel::SetPrune(bool prune, bool force)
+void OptionsModel::SetPruneEnabled(bool prune, bool force)
 {
     QSettings settings;
     settings.setValue("bPrune", prune);
@@ -252,6 +252,16 @@ void OptionsModel::SetPrune(bool prune, bool force)
     }
 }
 
+void OptionsModel::SetPruneTargetGB(int prune_target_gb, bool force)
+{
+    const bool prune = prune_target_gb > 0;
+    if (prune) {
+        QSettings settings;
+        settings.setValue("nPruneSize", prune_target_gb);
+    }
+    SetPruneEnabled(prune, force);
+}
+
 // read QSettings values and return them
 QVariant OptionsModel::data(const QModelIndex & index, int role) const
 {
diff --git a/src/qt/optionsmodel.h b/src/qt/optionsmodel.h
index 5791b47f28..5089a40509 100644
--- a/src/qt/optionsmodel.h
+++ b/src/qt/optionsmodel.h
@@ -73,7 +73,8 @@ public:
     const QString& getOverriddenByCommandLine() { return strOverriddenByCommandLine; }
 
     /* Explicit setters */
-    void SetPrune(bool prune, bool force = false);
+    void SetPruneEnabled(bool prune, bool force = false);
+    void SetPruneTargetGB(int prune_target_gb, bool force = false);
 
     /* Restart flag helper */
     void setRestartRequired(bool fRequired);