Couple de valeur en cle primaire et cle etrangere.

Bonsoir, je suis en train de construire une base de donnees, j'ai le couple(NumACC,NumVeh) en cle primaire en meme temps qui est cle etrangere dans la table 'Implication'... Mais en tant cles etrangeres ils ne marchent pas dans la table 'Implication'...

drop database Assurance ;
create database Assurance;
use Assurance;
create table Client
(NumClient Varchar (30), Nom varchar (30), Adresse varchar(30));
create table Vehicule
(NumVeh int, Marque varchar (40), Modele varchar(30), Annee varchar(40),
Cylindre int, Signataire varchar(30),NumCtr int, NumClient varchar(30), Prix decimal);
create table Accident
(NumACC int, DateACC date, montant decimal);
create table Contrat
(Signataire varchar (30), NumCtr int, TypeC varchar(30), DateDesign date);
create table Implication
(NumACC int, NumVeh int, NumClient varchar(30));

alter table Client add
constraint pk_Client primary key(NumClient);

alter table Vehicule add
constraint pk_Vehicule primary key(NumVeh);



alter table Contrat add
constraint pk_Contrat primary key(Signataire,NumCtr);

alter table Accident add
constraint pk_Accident primary key(NumACC);


alter table Implication add
constraint pk_Implication primary key(NumACC,NumVeh);

alter table Vehicule add
constraint fk_Vehicule_Contrat foreign key(Signataire,NumCtr) references Contrat(Signataire,NumCtr);

alter table Vehicule add
constraint fk_Vehicule_Client foreign key(NumClient) references Client(NumClient);

alter table Implication add
constraint fk_Implication_Accident foreign key(NumACC) references Accident(NumACC);

alter table Implication add
constraint fk_Implication_Vehicule foreign key(NumVeh) references Vehicule(NumVeh);