diff --git a/dlls/ntdll/ntdll.spec b/dlls/ntdll/ntdll.spec
index 248ae72a011..b9acb120844 100644
--- a/dlls/ntdll/ntdll.spec
+++ b/dlls/ntdll/ntdll.spec
@@ -572,7 +572,7 @@
 @ stdcall RtlDecodeSystemPointer(ptr) RtlDecodePointer
 @ stdcall RtlDecompressBuffer(long ptr long ptr long ptr)
 @ stdcall RtlDecompressFragment(long ptr long ptr long long ptr ptr)
-@ stub RtlDefaultNpAcl
+@ stdcall RtlDefaultNpAcl(ptr)
 @ stub RtlDelete
 @ stdcall RtlDeleteAce(ptr long)
 @ stdcall RtlDeleteAtomFromAtomTable(ptr long)
diff --git a/dlls/ntdll/sec.c b/dlls/ntdll/sec.c
index 0d45bbf02aa..eccfc82ce8c 100644
--- a/dlls/ntdll/sec.c
+++ b/dlls/ntdll/sec.c
@@ -1718,3 +1718,14 @@ NTSTATUS WINAPI RtlConvertToAutoInheritSecurityObject(
 
     return STATUS_NOT_IMPLEMENTED;
 }
+
+/******************************************************************************
+ * RtlDefaultNpAcl (NTDLL.@)
+ */
+NTSTATUS WINAPI RtlDefaultNpAcl(PACL *pAcl)
+{
+    FIXME("%p - stub\n", pAcl);
+
+    *pAcl = NULL;
+    return STATUS_SUCCESS;
+}