diff --git a/dlls/ntdll/nt.c b/dlls/ntdll/nt.c
index 6a919aa5595..30d3e34f33d 100644
--- a/dlls/ntdll/nt.c
+++ b/dlls/ntdll/nt.c
@@ -348,7 +348,7 @@ NTSTATUS WINAPI NtQueryInformationToken(
 
                 groups->GroupCount = tg->count;
                 memcpy( sids, (char *)buffer + non_sid_portion,
-                        reply->user_len - non_sid_portion - FIELD_OFFSET( TOKEN_GROUPS, Groups[tg->count] ));
+                        reply->user_len - FIELD_OFFSET( TOKEN_GROUPS, Groups[tg->count] ));
 
                 for (i = 0; i < tg->count; i++)
                 {