diff --git a/include/wx/msw/private/darkmode.h b/include/wx/msw/private/darkmode.h
index 2ef0d1b3fd..db3897d44b 100644
--- a/include/wx/msw/private/darkmode.h
+++ b/include/wx/msw/private/darkmode.h
@@ -17,6 +17,7 @@ namespace wxMSWDarkMode
 
 // Return true if the application is using dark mode: note that this will only
 // be the case if wxApp::MSWEnableDarkMode() was called.
+WXDLLIMPEXP_CORE
 bool IsActive();
 
 // Enable dark mode for the given TLW if appropriate.