diff --git a/reactos/hal/halx86/generic/bios.c b/reactos/hal/halx86/generic/bios.c
index 9103effe84a..815062b0685 100644
--- a/reactos/hal/halx86/generic/bios.c
+++ b/reactos/hal/halx86/generic/bios.c
@@ -424,7 +424,7 @@ HalpRestoreIopm(VOID)
     //
     // Set default state
     //
-    RtlFillMemory(HalpSavedIoMap, 0xFF, IOPM_FULL_SIZE);
+    RtlFillMemory(HalpSavedIoMap, IOPM_FULL_SIZE, 0xFF);
 
     //
     // Restore the backed up copy, and initialize it