diff --git a/sdk/xtdk/rtlfuncs.h b/sdk/xtdk/rtlfuncs.h
index f53c22c..3da0b38 100644
--- a/sdk/xtdk/rtlfuncs.h
+++ b/sdk/xtdk/rtlfuncs.h
@@ -71,7 +71,7 @@ XTCDECL
 INT
 RtlWideStringCompare(IN CONST PWCHAR String1,
                      IN CONST PWCHAR String2,
-                     IN CONST ULONG Length);
+                     IN CONST SIZE_T Length);
 
 XTCDECL
 PWCHAR
diff --git a/xtoskrnl/rtl/widestr.c b/xtoskrnl/rtl/widestr.c
index 467f4ff..458dd99 100644
--- a/xtoskrnl/rtl/widestr.c
+++ b/xtoskrnl/rtl/widestr.c
@@ -29,9 +29,9 @@ XTCDECL
 INT
 RtlWideStringCompare(IN CONST PWCHAR String1,
                      IN CONST PWCHAR String2,
-                     IN CONST ULONG Length)
+                     IN CONST SIZE_T Length)
 {
-    ULONG Index;
+    SIZE_T Index;
 
     /* Iterate through the strings */
     for(Index = 0; ; Index++) {