diff --git a/packages/transaction-manager/lib/TxMonitor.ts b/packages/transaction-manager/lib/TxMonitor.ts
index 45c621ade6..3de02f2e52 100644
--- a/packages/transaction-manager/lib/TxMonitor.ts
+++ b/packages/transaction-manager/lib/TxMonitor.ts
@@ -10,6 +10,8 @@ type AttemptWithReceipt = { attempt: Attempt; receipt: TransactionReceipt }
 
 export class TxMonitor {
     private readonly transactionManager: TransactionManager
+    private locked = false
+    private pendingBlockPromises: PromiseWithResolvers<void>[] = []
 
     constructor(transactionManager: TransactionManager) {
         this.transactionManager = transactionManager
@@ -17,6 +19,30 @@ export class TxMonitor {
     }
 
     private async onNewBlock(block: LatestBlock) {
+        if (this.locked) {
+            const pending = promiseWithResolvers<void>()
+            this.pendingBlockPromises.push(pending)
+            try {
+                await pending.promise
+            } catch {
+                // A more recent block came while we were waiting, abort.
+                return
+            }
+        }
+
+        this.locked = true
+        try {
+            await this.handleNewBlock(block)
+        } catch (error) {
+            console.error("Error in handleNewBlock: ", error)
+        }
+        this.locked = false
+
+        this.pendingBlockPromises.pop()?.resolve()
+        this.pendingBlockPromises.forEach((p) => p.reject())
+    }
+
+    private async handleNewBlock(block: LatestBlock) {
         const transactions = this.transactionManager.transactionRepository.getNotFinalizedTransactions()
 
         const promises = transactions.map(async (transaction) => {