diff --git a/src/effects/nyquist/Nyquist.cpp b/src/effects/nyquist/Nyquist.cpp
index 00590c746..0fb4307a0 100644
--- a/src/effects/nyquist/Nyquist.cpp
+++ b/src/effects/nyquist/Nyquist.cpp
@@ -40,6 +40,7 @@ effects from this one class.
 #include <wx/datetime.h>
 #include <wx/intl.h>
 #include <wx/log.h>
+#include <wx/scrolwin.h>
 #include <wx/sizer.h>
 #include <wx/slider.h>
 #include <wx/sstream.h>
diff --git a/src/menus/HelpMenus.cpp b/src/menus/HelpMenus.cpp
index 57aafd2e3..d203f7a37 100644
--- a/src/menus/HelpMenus.cpp
+++ b/src/menus/HelpMenus.cpp
@@ -13,6 +13,7 @@
 #include "../commands/CommandContext.h"
 #include "../commands/CommandManager.h"
 #include "../widgets/HelpSystem.h"
+#include "../widgets/LinkingHtmlWindow.h"
 
 #if defined(EXPERIMENTAL_CRASH_REPORT)
 #include <wx/debugrpt.h>
diff --git a/src/widgets/ErrorDialog.h b/src/widgets/ErrorDialog.h
index 04b5e242d..7d554e7e7 100644
--- a/src/widgets/ErrorDialog.h
+++ b/src/widgets/ErrorDialog.h
@@ -16,7 +16,6 @@
 
 #include <wx/defs.h>
 #include <wx/msgdlg.h> // to inherit
-#include "LinkingHtmlWindow.h"
 #include "wxPanelWrapper.h"
 
 class AudacityProject;
@@ -43,28 +42,6 @@ private:
    DECLARE_EVENT_TABLE()
 };
 
-// Helper class to make browser "simulate" a modal dialog
-class HtmlTextHelpDialog final : public BrowserDialog
-{
-public:
-   HtmlTextHelpDialog(wxWindow *pParent, const wxString &title)
-      : BrowserDialog{ pParent, title }
-   {
-#if !wxCHECK_VERSION(3, 0, 0)
-      MakeModal( true );
-#endif
-   }
-   virtual ~HtmlTextHelpDialog()
-   {
-#if !wxCHECK_VERSION(3, 0, 0)
-      MakeModal( false );
-#endif
-      // On Windows, for some odd reason, the Audacity window will be sent to
-      // the back.  So, make sure that doesn't happen.
-      GetParent()->Raise();
-   }
-};
-
 /// Displays an error dialog with a button that offers help
 void ShowErrorDialog(wxWindow *parent,
                      const wxString &dlogTitle,
diff --git a/src/widgets/HelpSystem.cpp b/src/widgets/HelpSystem.cpp
index fa1149966..a83f0cdbf 100644
--- a/src/widgets/HelpSystem.cpp
+++ b/src/widgets/HelpSystem.cpp
@@ -51,6 +51,32 @@ const wxString HelpSystem::HelpServerManDir = wxT("/man/");
 const wxString HelpSystem::LocalHelpManDir = wxT("/man/");
 const wxString HelpSystem::ReleaseSuffix = wxT(".html");
 
+namespace {
+
+// Helper class to make browser "simulate" a modal dialog
+class HtmlTextHelpDialog final : public BrowserDialog
+{
+public:
+   HtmlTextHelpDialog(wxWindow *pParent, const wxString &title)
+      : BrowserDialog{ pParent, title }
+   {
+#if !wxCHECK_VERSION(3, 0, 0)
+      MakeModal( true );
+#endif
+   }
+   virtual ~HtmlTextHelpDialog()
+   {
+#if !wxCHECK_VERSION(3, 0, 0)
+      MakeModal( false );
+#endif
+      // On Windows, for some odd reason, the Audacity window will be sent to
+      // the back.  So, make sure that doesn't happen.
+      GetParent()->Raise();
+   }
+};
+
+}
+
 /// Mostly we use this so that we have the code for resizability
 /// in one place.  Other considerations like screen readers are also
 /// handled by having the code in one place.