diff --git a/.changeset/blue-needles-clap.md b/.changeset/blue-needles-clap.md
new file mode 100644
index 0000000000000..fccbfa51e50c8
--- /dev/null
+++ b/.changeset/blue-needles-clap.md
@@ -0,0 +1,5 @@
+---
+"@eth-optimism/data-transport-layer": patch
+---
+
+Account for the off by one with regards to the l2geth block number and the CTC index
diff --git a/packages/data-transport-layer/src/services/server/service.ts b/packages/data-transport-layer/src/services/server/service.ts
index b81ac71603d1b..b061e9d571bba 100644
--- a/packages/data-transport-layer/src/services/server/service.ts
+++ b/packages/data-transport-layer/src/services/server/service.ts
@@ -189,7 +189,7 @@ export class L1TransportServer extends BaseService<L1TransportServerOptions> {
             break
           case 'l2':
             currentL2Block = await this.state.db.getLatestUnconfirmedTransaction()
-            highestL2BlockNumber = await this.state.db.getHighestSyncedUnconfirmedBlock()
+            highestL2BlockNumber = (await this.state.db.getHighestSyncedUnconfirmedBlock()) - 1
             break
           default:
             throw new Error(`Unknown transaction backend ${backend}`)