diff --git a/backend/src/middleware/validation.js b/backend/src/middleware/validation.js
index 4cd7232..42ec460 100644
--- a/backend/src/middleware/validation.js
+++ b/backend/src/middleware/validation.js
@@ -399,12 +399,12 @@ function validateRequest(req, res, next) {
     message: e.msg,
   }));
 
-  const isContributionsPath = Boolean(
-    (req.originalUrl && req.originalUrl.includes('/contributions')) ||
-    (req.baseUrl && req.baseUrl.includes('/contributions')) ||
-    (req.path && req.path.includes('/contributions'))
+  const usesUnprocessableEntity = Boolean(
+    (req.originalUrl && (req.originalUrl.includes('/contributions') || req.originalUrl.includes('/withdrawals'))) ||
+    (req.baseUrl && (req.baseUrl.includes('/contributions') || req.baseUrl.includes('/withdrawals'))) ||
+    (req.path && (req.path.includes('/contributions') || req.path.includes('/withdrawals')))
   );
-  const statusCode = isContributionsPath ? 422 : 400;
+  const statusCode = usesUnprocessableEntity ? 422 : 400;
 
   return res.status(statusCode).json({
     error: {
diff --git a/backend/src/routes/withdrawals.test.js b/backend/src/routes/withdrawals.test.js
index f36c5df..b55b6d9 100644
--- a/backend/src/routes/withdrawals.test.js
+++ b/backend/src/routes/withdrawals.test.js
@@ -140,6 +140,26 @@ test('POST /api/withdrawals/request creates pending request and logs event', asy
   assert.ok(calls.some((c) => c.includes('INSERT INTO stellar_transactions')));
 });
 
+test('POST /api/withdrawals/request rejects an invalid Stellar public key with 422', async () => {
+  const { app, cleanup } = buildApp({
+    queryImpl: async (text) => {
+      if (text.includes('FROM campaigns WHERE id')) {
+        return { rows: [campaignRow()] };
+      }
+      return { rows: [] };
+    },
+  });
+
+  const response = await request(app)
+    .post('/api/withdrawals/request')
+    .set('Authorization', 'Bearer token')
+    .send({ campaign_id: '11111111-1111-1111-1111-111111111111', destination_key: 'not-a-valid-key', amount: '10.0000000' });
+
+  cleanup();
+  assert.equal(response.status, 422);
+  assert.match(response.body.error.message, /destination_key must be a valid Stellar public key/);
+});
+
 test('POST /api/withdrawals/request returns 400 for failed campaigns', async () => {
   const { app, cleanup } = buildApp({
     role: 'admin',