diff --git a/app/dashboard/actions.ts b/app/dashboard/actions.ts
index 5ab2590..e37ef5f 100644
--- a/app/dashboard/actions.ts
+++ b/app/dashboard/actions.ts
@@ -74,17 +74,30 @@ export async function updateMinecraftName(form: FormData) {
   const mcName = (form.get("mcName") as string).trim();
   if (!/^[A-Za-z0-9_]{3,16}$/.test(mcName)) throw new Error("invalid");
 
-  await prisma.user.upsert({
+  const user = await prisma.user.findUnique({
     where: { email: session.user!.email! },
-    update: { mcName },
-    create: {
-      email: session.user!.email!,
-      name: session.user!.name,
-      image: session.user!.image,
-      mcName,
-    },
   });
 
+  if (!user) {
+    await prisma.user.create({
+      data: {
+        email: session.user!.email!,
+        name: session.user!.name,
+        image: session.user!.image,
+        mcName,
+      },
+    });
+  } else {
+    if (user.mcName) {
+      throw new Error("Le pseudo Minecraft ne peut pas être modifié après avoir été défini.");
+    }
+
+    await prisma.user.update({
+      where: { email: session.user!.email! },
+      data: { mcName },
+    });
+  }
+
   revalidatePath("/dashboard");
   revalidatePath("/");
-}
\ No newline at end of file
+}
diff --git a/app/dashboard/profil/page.tsx b/app/dashboard/profil/page.tsx
index 59747d9..5d34bb3 100644
--- a/app/dashboard/profil/page.tsx
+++ b/app/dashboard/profil/page.tsx
@@ -60,13 +60,15 @@ export default async function ProfilPage() {
               placeholder="Pseudo MC"
               required
               pattern="[A-Za-z0-9_]{3,16}"
-              className="input pl-12"
+              disabled={Boolean(user?.mcName)}
+              className="input pl-12 disabled:opacity-60"
             />
           </div>
 
           <button
             type="submit"
-            className="rounded bg-indigo-600 px-4 py-2 text-sm font-medium hover:bg-indigo-700"
+            disabled={Boolean(user?.mcName)}
+            className="rounded bg-indigo-600 px-4 py-2 text-sm font-medium hover:bg-indigo-700 disabled:opacity-50"
           >
             Enregistrer
           </button>