diff --git a/dlls/ntdll/nt.c b/dlls/ntdll/nt.c
index 5c8b7fdcee..a18dfae0e5 100644
--- a/dlls/ntdll/nt.c
+++ b/dlls/ntdll/nt.c
@@ -2340,7 +2340,7 @@ NTSTATUS WINAPI NtQuerySystemInformation(
 NTSTATUS WINAPI NtQuerySystemInformationEx(SYSTEM_INFORMATION_CLASS SystemInformationClass,
     void *Query, ULONG QueryLength, void *SystemInformation, ULONG Length, ULONG *ResultLength)
 {
-    ULONG len;
+    ULONG len = 0;
     NTSTATUS ret = STATUS_NOT_IMPLEMENTED;
 
     TRACE("(0x%08x,%p,%u,%p,%u,%p) stub\n", SystemInformationClass, Query, QueryLength, SystemInformation,