diff --git a/include/wx/filename.h b/include/wx/filename.h
index 7eff2e8783..023366e020 100644
--- a/include/wx/filename.h
+++ b/include/wx/filename.h
@@ -87,7 +87,7 @@ enum
 
 #if wxUSE_LONGLONG
 // error code of wxFileName::GetSize()
-extern wxULongLong wxInvalidSize;
+extern WXDLLIMPEXP_DATA_BASE(const wxULongLong) wxInvalidSize;
 #endif // wxUSE_LONGLONG
 
 
diff --git a/samples/console/console.cpp b/samples/console/console.cpp
index 04c23b8225..abb4da0f22 100644
--- a/samples/console/console.cpp
+++ b/samples/console/console.cpp
@@ -4215,6 +4215,7 @@ static void TestSemaphore()
     #include "wx/snglinst.h"
 #endif // TEST_SNGLINST
 
+#include "wx/filename.h"
 int main(int argc, char **argv)
 {
 #if wxUSE_UNICODE
diff --git a/src/common/filename.cpp b/src/common/filename.cpp
index 2d583d2719..7846362846 100644
--- a/src/common/filename.cpp
+++ b/src/common/filename.cpp
@@ -140,7 +140,7 @@
 
 
 #if wxUSE_LONGLONG
-wxULongLong wxInvalidSize = (unsigned)-1;
+extern const wxULongLong wxInvalidSize = (unsigned)-1;
 #endif // wxUSE_LONGLONG