diff --git a/common/haswell_shared/hw-gfx-gma-power_and_clocks_haswell.adb b/common/haswell_shared/hw-gfx-gma-power_and_clocks_haswell.adb
index 555a9b7..e83efa9 100644
--- a/common/haswell_shared/hw-gfx-gma-power_and_clocks_haswell.adb
+++ b/common/haswell_shared/hw-gfx-gma-power_and_clocks_haswell.adb
@@ -111,8 +111,10 @@
          if Enabled then
             if Config.Has_IPS_CTL_Mailbox then
                GT_Mailbox_Write (DISPLAY_IPS_CONTROL, 0);
-               -- May take up to 42ms.
-               Registers.Wait_Unset_Mask (Registers.IPS_CTL, IPS_CTL_ENABLE);
+               Registers.Wait_Unset_Mask
+                 (Register => Registers.IPS_CTL,
+                  Mask     => IPS_CTL_ENABLE,
+                  TOut_MS  => 42);
             else
                Registers.Unset_Mask (Registers.IPS_CTL, IPS_CTL_ENABLE);
             end if;