diff --git a/src/Audacity.h b/src/Audacity.h
index 3a7f7c073..48759dc74 100644
--- a/src/Audacity.h
+++ b/src/Audacity.h
@@ -88,7 +88,4 @@
                               AUDACITY_QUOTE( AUDACITY_MODLEVEL )
 #endif
 
-
-class wxWindow;
-
 #endif // __AUDACITY_H__
diff --git a/src/Benchmark.h b/src/Benchmark.h
index 35022e8f7..9bedfdff1 100644
--- a/src/Benchmark.h
+++ b/src/Benchmark.h
@@ -11,6 +11,7 @@
 #ifndef __AUDACITY_BENCHMARK__
 #define __AUDACITY_BENCHMARK__
 
+class wxWindow;
 class AudacityProject;
 
 void RunBenchmark( wxWindow *parent, AudacityProject &project );
diff --git a/src/LangChoice.h b/src/LangChoice.h
index 1788ddb1a..57e3fd65c 100644
--- a/src/LangChoice.h
+++ b/src/LangChoice.h
@@ -16,6 +16,7 @@
 #define __AUDACITY_LANG_CHOICE__
 
 class wxString;
+class wxWindow;
 
 wxString ChooseLanguage(wxWindow *parent);
 
diff --git a/src/TempDirectory.h b/src/TempDirectory.h
index c795f7df4..a6c67dda6 100644
--- a/src/TempDirectory.h
+++ b/src/TempDirectory.h
@@ -14,6 +14,8 @@
 #include "Audacity.h"
 #include "audacity/Types.h"
 
+class wxWindow;
+
 namespace TempDirectory
 {
    wxString TempDir();
diff --git a/src/widgets/Warning.h b/src/widgets/Warning.h
index 5445e54ad..5587c8f87 100644
--- a/src/widgets/Warning.h
+++ b/src/widgets/Warning.h
@@ -15,6 +15,7 @@
 
 #include <wx/defs.h>
 class wxString;
+class wxWindow;
 class TranslatableString;
 
 // "Don't show this warning again"