diff --git a/src/openrct2-ui/windows/Sign.cpp b/src/openrct2-ui/windows/Sign.cpp
index 7fd1ed8659..a10206e2ea 100644
--- a/src/openrct2-ui/windows/Sign.cpp
+++ b/src/openrct2-ui/windows/Sign.cpp
@@ -322,10 +322,7 @@ static void window_sign_paint(rct_window* w, rct_drawpixelinfo* dpi)
  */
 static void window_sign_viewport_rotate(rct_window* w)
 {
-    rct_viewport* view = w->viewport;
-    w->viewport = nullptr;
-
-    view->width = 0;
+    w->RemoveViewport();
 
     auto banner = GetBanner(w->number);
 
diff --git a/src/openrct2/interface/Window_internal.cpp b/src/openrct2/interface/Window_internal.cpp
index 0a0d0e738e..675db961d9 100644
--- a/src/openrct2/interface/Window_internal.cpp
+++ b/src/openrct2/interface/Window_internal.cpp
@@ -42,3 +42,12 @@ void rct_window::Invalidate()
 {
     gfx_set_dirty_blocks({ windowPos, windowPos + ScreenCoordsXY{ width, height } });
 }
+
+void rct_window::RemoveViewport()
+{
+    if (viewport == nullptr)
+        return;
+
+    viewport->width = 0;
+    viewport = nullptr;
+}
diff --git a/src/openrct2/interface/Window_internal.h b/src/openrct2/interface/Window_internal.h
index 2a882649d6..039d078ed1 100644
--- a/src/openrct2/interface/Window_internal.h
+++ b/src/openrct2/interface/Window_internal.h
@@ -94,6 +94,7 @@ struct rct_window
     void SetLocation(const CoordsXYZ& coords);
     void ScrollToViewport();
     void Invalidate();
+    void RemoveViewport();
 };
 
 // rct2: 0x01420078