diff --git a/dlls/advapi32/advapi32.spec b/dlls/advapi32/advapi32.spec
index 21357fa6871..38342dc76fe 100644
--- a/dlls/advapi32/advapi32.spec
+++ b/dlls/advapi32/advapi32.spec
@@ -25,7 +25,7 @@
 @ stdcall AddAuditAccessAceEx(ptr long long long ptr long long)
 # @ stub AddAuditAccessObjectAce
 # @ stub AddConditionalAce
-# @ stub AddMandatoryAce
+@ stdcall AddMandatoryAce(ptr long long long ptr)
 # @ stub AddUsersToEncryptedFileEx
 # @ stub ADVAPI32_1000
 # @ stub AddUsersToEncryptedFile
diff --git a/dlls/advapi32/security.c b/dlls/advapi32/security.c
index 954a1c5787f..8e2f39c4e60 100644
--- a/dlls/advapi32/security.c
+++ b/dlls/advapi32/security.c
@@ -1567,6 +1567,12 @@ BOOL WINAPI AddAce(
     return set_ntstatus(RtlAddAce(pAcl, dwAceRevision, dwStartingAceIndex, pAceList, nAceListLength));
 }
 
+BOOL WINAPI AddMandatoryAce(ACL *acl, DWORD ace_revision, DWORD ace_flags, DWORD mandatory_policy, PSID label_sid)
+{
+    FIXME("%p %x %x %x %p - stub\n", acl, ace_revision, ace_flags, mandatory_policy, label_sid);
+    return FALSE;
+}
+
 /******************************************************************************
  * DeleteAce [ADVAPI32.@]
  */