diff --git a/reactos/sdk/lib/rtl/unicode.c b/reactos/sdk/lib/rtl/unicode.c
index a6185b9c1dc..99da382ea6e 100644
--- a/reactos/sdk/lib/rtl/unicode.c
+++ b/reactos/sdk/lib/rtl/unicode.c
@@ -1367,7 +1367,7 @@ RtlIsTextUnicode(CONST VOID* buf, INT len, INT* pf)
             else
                 weight = 1;
 
-            if (flags & IS_TEXT_UNICODE_DBCS_LEADBYTE)
+            if (pf && (*pf & IS_TEXT_UNICODE_DBCS_LEADBYTE))
                 out_flags |= IS_TEXT_UNICODE_DBCS_LEADBYTE;
         }
     }