diff --git a/source/interposer/interposer-x11.cpp b/source/interposer/interposer-x11.cpp
index 1189935d2..863012c79 100644
--- a/source/interposer/interposer-x11.cpp
+++ b/source/interposer/interposer-x11.cpp
@@ -65,11 +65,13 @@ int XMapWindow(Display* display, Window w)
     {
         CARLA_SAFE_ASSERT_RETURN(winIdStr[0] != '\0', real_XMapWindow(display, w));
 
-        const long long winId(std::strtoll(winIdStr, nullptr, 16));
-        CARLA_SAFE_ASSERT_RETURN(winId >= 0, real_XMapWindow(display, w));
+        const long long winIdLL(std::strtoll(winIdStr, nullptr, 16));
+        CARLA_SAFE_ASSERT_RETURN(winIdLL >= 0, real_XMapWindow(display, w));
 
-        carla_stdout("Transient hint correctly applied before mapping window");
+        const Window winId(static_cast<Window>(winIdLL));
         XSetTransientForHint(display, w, static_cast<Window>(winId));
+
+        carla_stdout("Transient hint correctly applied before mapping window");
     }
 
     return real_XMapWindow(display, w);