diff --git a/common/hw-gfx-gma.adb b/common/hw-gfx-gma.adb
index 0a80d6b..dfe986f 100644
--- a/common/hw-gfx-gma.adb
+++ b/common/hw-gfx-gma.adb
@@ -695,7 +695,7 @@
    with
       Pre => Is_Initialized
    is
-      GGC_Reg : constant :=
+      GGC_Reg : constant PCI.Index :=
         (if Config.Gen_G45 or Config.CPU_Ironlake then 16#52# else 16#50#);
       GGC : Word16;
    begin