diff --git a/dlls/user32/win.c b/dlls/user32/win.c
index 0bb9fd9cba7..a29e3a1d9bb 100644
--- a/dlls/user32/win.c
+++ b/dlls/user32/win.c
@@ -742,7 +742,7 @@ HWND WIN_GetFullHandle( HWND hwnd )
  *
  * Change the owner of a window.
  */
-HWND WIN_SetOwner( HWND hwnd, HWND owner )
+static HWND WIN_SetOwner( HWND hwnd, HWND owner )
 {
     WND *win = WIN_GetPtr( hwnd );
     HWND ret = 0;
diff --git a/dlls/user32/win.h b/dlls/user32/win.h
index 81b08fc95ea..1f51fd63314 100644
--- a/dlls/user32/win.h
+++ b/dlls/user32/win.h
@@ -91,7 +91,6 @@ extern HWND WIN_GetFullHandle( HWND hwnd ) DECLSPEC_HIDDEN;
 extern HWND WIN_IsCurrentProcess( HWND hwnd ) DECLSPEC_HIDDEN;
 extern HWND WIN_IsCurrentThread( HWND hwnd ) DECLSPEC_HIDDEN;
 extern UINT win_set_flags( HWND hwnd, UINT set_mask, UINT clear_mask ) DECLSPEC_HIDDEN;
-extern HWND WIN_SetOwner( HWND hwnd, HWND owner ) DECLSPEC_HIDDEN;
 extern ULONG WIN_SetStyle( HWND hwnd, ULONG set_bits, ULONG clear_bits ) DECLSPEC_HIDDEN;
 extern BOOL WIN_GetRectangles( HWND hwnd, enum coords_relative relative, RECT *rectWindow, RECT *rectClient ) DECLSPEC_HIDDEN;
 extern void map_window_region( HWND from, HWND to, HRGN hrgn ) DECLSPEC_HIDDEN;