diff --git a/ApplicationLibCode/UserInterface/RiuMainWindow.cpp b/ApplicationLibCode/UserInterface/RiuMainWindow.cpp
index d96b230a50..7bf1d33ca5 100644
--- a/ApplicationLibCode/UserInterface/RiuMainWindow.cpp
+++ b/ApplicationLibCode/UserInterface/RiuMainWindow.cpp
@@ -335,6 +335,8 @@ void RiuMainWindow::cleanupGuiCaseClose()
 //--------------------------------------------------------------------------------------------------
 void RiuMainWindow::cleanupGuiBeforeProjectClose()
 {
+    m_mdiArea->closeAllSubWindows();
+
     setPdmRoot( nullptr );
 
     cleanupGuiCaseClose();
diff --git a/ApplicationLibCode/UserInterface/RiuPlotMainWindow.cpp b/ApplicationLibCode/UserInterface/RiuPlotMainWindow.cpp
index 4945e30cfe..43af07272e 100644
--- a/ApplicationLibCode/UserInterface/RiuPlotMainWindow.cpp
+++ b/ApplicationLibCode/UserInterface/RiuPlotMainWindow.cpp
@@ -245,6 +245,8 @@ void RiuPlotMainWindow::initializeGuiNewProjectLoaded()
 //--------------------------------------------------------------------------------------------------
 void RiuPlotMainWindow::cleanupGuiBeforeProjectClose()
 {
+    m_mdiArea->closeAllSubWindows();
+
     setPdmRoot( nullptr );
 
     for ( auto pdmUiPropertyView : m_propertyViews )