diff --git a/contracts/vault/VaultBase.sol b/contracts/vault/VaultBase.sol
index c7baccb..c79dd7c 100644
--- a/contracts/vault/VaultBase.sol
+++ b/contracts/vault/VaultBase.sol
@@ -150,10 +150,17 @@ abstract contract VaultBase {
     Recipient recipient,
     uint128 amount
   ) internal {
-    Balance storage balance = _balances[controller][context][recipient];
+    Balance memory balance = _balances[controller][context][recipient];
     require(amount <= balance.available, InsufficientBalance());
+
     balance.available -= amount;
     balance.designated += amount;
+
+    Flow memory flow = _flows[controller][context][recipient];
+    Lock memory lock = _locks[controller][context];
+    _checkFlowInvariant(balance, lock, flow);
+
+    _balances[controller][context][recipient] = balance;
   }
 
   function _lockup(
diff --git a/test/Vault.tests.js b/test/Vault.tests.js
index 3f6a4cd..5866cef 100644
--- a/test/Vault.tests.js
+++ b/test/Vault.tests.js
@@ -600,6 +600,15 @@ describe("Vault", function () {
         ).to.be.revertedWith("InsufficientBalance")
       })
 
+      it("cannot designate tokens that are flowing", async function () {
+        await vault.flow(context, sender, receiver, 5)
+        setAutomine(true)
+        await vault.designate(context, sender, 500)
+        await expect(vault.designate(context, sender, 1)).to.be.revertedWith(
+          "InsufficientBalance"
+        )
+      })
+
       it("cannot burn tokens that are flowing", async function () {
         await vault.flow(context, sender, receiver, 5)
         setAutomine(true)