diff --git a/app/api/missions/route.ts b/app/api/missions/route.ts
index 5c373a39..8e36ffde 100644
--- a/app/api/missions/route.ts
+++ b/app/api/missions/route.ts
@@ -170,7 +170,7 @@ export async function POST(request: Request) {
       const updatedMission = await prisma.mission.update({
         where: { id: existingMission.id },
         data: {
-          leantimeProjectId: body.leantimeProjectId || null,
+          leantimeProjectId: body.leantimeProjectId ? String(body.leantimeProjectId) : null,
           outlineCollectionId: body.documentationCollectionId || null,
           rocketChatChannelId: body.rocketchatChannelId || null,
           giteaRepositoryUrl: body.gitRepoUrl || null,