diff --git a/plasma_framework/contracts/src/framework/ExitGameController.sol b/plasma_framework/contracts/src/framework/ExitGameController.sol
index d5fc1f4c2..989c03664 100644
--- a/plasma_framework/contracts/src/framework/ExitGameController.sol
+++ b/plasma_framework/contracts/src/framework/ExitGameController.sol
@@ -104,6 +104,7 @@ contract ExitGameController is ExitGameRegistry {
      *         priority queue to enforce the priority of exit during 'processExits'
      * @dev emits ExitQueued event, which can be used to back trace the priority inside the queue
      * @dev Caller of this function should add "pragma experimental ABIEncoderV2;" on top of file
+     * @dev Priority (exitableAt, txPos, exitId) must be unique per queue. Do not enqueue when the same priority is already in the queue.
      * @param vaultId Vault ID of the vault that stores exiting funds
      * @param token Token for the exit
      * @param exitableAt The earliest time a specified exit can be processed
@@ -133,6 +134,7 @@ contract ExitGameController is ExitGameRegistry {
         queue.insert(priority);
 
         bytes32 delegationKey = getDelegationKey(priority, vaultId, token);
+        require(address(delegations[delegationKey]) == address(0), "The same priority is already enqueued");
         delegations[delegationKey] = exitProcessor;
 
         emit ExitQueued(exitId, priority);
diff --git a/plasma_framework/test/src/framework/ExitGameController.test.js b/plasma_framework/test/src/framework/ExitGameController.test.js
index 84db6a122..b2ad5582b 100644
--- a/plasma_framework/test/src/framework/ExitGameController.test.js
+++ b/plasma_framework/test/src/framework/ExitGameController.test.js
@@ -134,7 +134,7 @@ contract('ExitGameController', () => {
             );
         });
 
-        it('can enqueue with the same exitable timestamp (priority) multiple times', async () => {
+        it('rejects when the same priority is already enqueued', async () => {
             await this.dummyExitGame.enqueue(
                 VAULT_ID,
                 this.dummyExit.token,
@@ -144,6 +144,23 @@ contract('ExitGameController', () => {
                 this.dummyExit.exitProcessor,
             );
 
+            await expectRevert(
+                this.dummyExitGame.enqueue(
+                    VAULT_ID,
+                    this.dummyExit.token,
+                    this.dummyExit.exitableAt,
+                    this.dummyExit.txPos,
+                    this.dummyExit.exitId,
+                    this.dummyExit.exitProcessor,
+                ),
+                'The same priority is already enqueued',
+            );
+        });
+
+        it('can enqueue with the exact same priority to different priority queue', async () => {
+            const vaultId2 = VAULT_ID + 1;
+            await this.controller.addExitQueue(vaultId2, this.dummyToken);
+
             await this.dummyExitGame.enqueue(
                 VAULT_ID,
                 this.dummyExit.token,
@@ -153,6 +170,47 @@ contract('ExitGameController', () => {
                 this.dummyExit.exitProcessor,
             );
 
+            await this.dummyExitGame.enqueue(
+                vaultId2,
+                this.dummyExit.token,
+                this.dummyExit.exitableAt,
+                this.dummyExit.txPos,
+                this.dummyExit.exitId,
+                this.dummyExit.exitProcessor,
+            );
+
+            const key = exitQueueKey(VAULT_ID, this.dummyToken);
+            const priorityQueueAddress = await this.controller.exitsQueues(key);
+            const priorityQueue = await PriorityQueue.at(priorityQueueAddress);
+            expect(await priorityQueue.currentSize()).to.be.bignumber.equal(new BN(1));
+
+            const key2 = exitQueueKey(vaultId2, this.dummyToken);
+            const priorityQueueAddress2 = await this.controller.exitsQueues(key2);
+            const priorityQueue2 = await PriorityQueue.at(priorityQueueAddress2);
+            expect(await priorityQueue2.currentSize()).to.be.bignumber.equal(new BN(1));
+        });
+
+        it('can enqueue with the same exitable timestamp and txPos but with different exitId multiple times to the same queue', async () => {
+            const exitId1 = 111111;
+            const exitId2 = 22222;
+            await this.dummyExitGame.enqueue(
+                VAULT_ID,
+                this.dummyExit.token,
+                this.dummyExit.exitableAt,
+                this.dummyExit.txPos,
+                exitId1,
+                this.dummyExit.exitProcessor,
+            );
+
+            await this.dummyExitGame.enqueue(
+                VAULT_ID,
+                this.dummyExit.token,
+                this.dummyExit.exitableAt,
+                this.dummyExit.txPos,
+                exitId2,
+                this.dummyExit.exitProcessor,
+            );
+
             const key = exitQueueKey(VAULT_ID, this.dummyToken);
             const priorityQueueAddress = await this.controller.exitsQueues(key);
             const priorityQueue = await PriorityQueue.at(priorityQueueAddress);