diff --git a/packages/protocol/contracts/L1/TaikoL1.sol b/packages/protocol/contracts/L1/TaikoL1.sol
index 04d59815355..580137155e4 100644
--- a/packages/protocol/contracts/L1/TaikoL1.sol
+++ b/packages/protocol/contracts/L1/TaikoL1.sol
@@ -237,7 +237,8 @@ contract TaikoL1 is EssentialContract, IHeaderSync, TaikoEvents {
     function getProposedBlock(
         uint256 id
     ) public view returns (TaikoData.ProposedBlock memory) {
-        return state.getProposedBlock(getConfig().maxNumBlocks, id);
+        return
+            LibProposing.getProposedBlock(state, getConfig().maxNumBlocks, id);
     }
 
     function getSyncedHeader(
diff --git a/packages/protocol/contracts/L1/libs/LibProposing.sol b/packages/protocol/contracts/L1/libs/LibProposing.sol
index 8525da78284..58879b3d5e2 100644
--- a/packages/protocol/contracts/L1/libs/LibProposing.sol
+++ b/packages/protocol/contracts/L1/libs/LibProposing.sol
@@ -140,6 +140,15 @@ library LibProposing {
         emit BlockProposed(state.nextBlockId++, meta);
     }
 
+    function getProposedBlock(
+        TaikoData.State storage state,
+        uint256 maxNumBlocks,
+        uint256 id
+    ) internal view returns (TaikoData.ProposedBlock storage) {
+        require(id > state.latestVerifiedId && id < state.nextBlockId, "L1:id");
+        return state.getProposedBlock(maxNumBlocks, id);
+    }
+
     function getBlockFee(
         TaikoData.State storage state,
         TaikoData.Config memory config
diff --git a/packages/protocol/test/L1/TaikoL1.test.ts b/packages/protocol/test/L1/TaikoL1.test.ts
index 5b25613a330..5a1d23f7fed 100644
--- a/packages/protocol/test/L1/TaikoL1.test.ts
+++ b/packages/protocol/test/L1/TaikoL1.test.ts
@@ -169,7 +169,9 @@ describe("integration:TaikoL1", function () {
         );
 
         l2Signer = await l2Provider.getSigner(
-            (await l2Provider.listAccounts())[0]
+            (
+                await l2Provider.listAccounts()
+            )[0]
         );
 
         const addressManager = await (
@@ -267,11 +269,10 @@ describe("integration:TaikoL1", function () {
     });
 
     describe("getProposedBlock()", function () {
-        it("proposed block does not exist", async function () {
-            const block = await taikoL1.getProposedBlock(123);
-            expect(block[0]).to.be.eq(ethers.constants.HashZero);
-            expect(block[1]).to.be.eq(ethers.constants.AddressZero);
-            expect(block[2]).to.be.eq(BigNumber.from(0));
+        it("reverts when id is not a valid proposed block in range", async function () {
+            await expect(taikoL1.getProposedBlock(123)).to.be.revertedWith(
+                "L1:id"
+            );
         });
     });
     describe("commitBlock() -> proposeBlock() integration", async function () {