diff --git a/src/tqtraylabel.cpp b/src/tqtraylabel.cpp
index 925ffd2..7df1d45 100644
--- a/src/tqtraylabel.cpp
+++ b/src/tqtraylabel.cpp
@@ -254,7 +254,7 @@ void TQTrayLabel::dock(void)
   Window wid = winId();
 
   // 1. GNOME and NET WM Specification
-  long l[5] = { CurrentTime, SYSTEM_TRAY_REQUEST_DOCK, wid, 0, 0 };
+  unsigned long l[5] = { CurrentTime, SYSTEM_TRAY_REQUEST_DOCK, wid, 0, 0 };
   sendMessage(display, mSysTray, mSysTray, "_NET_SYSTEM_TRAY_OPCODE",
               32, 0L, l, sizeof(l));