diff --git a/remix-debug/src/debugger/VmDebugger.js b/remix-debug/src/debugger/VmDebugger.js
index a21e5c5f61..896efdceea 100644
--- a/remix-debug/src/debugger/VmDebugger.js
+++ b/remix-debug/src/debugger/VmDebugger.js
@@ -196,7 +196,7 @@ class VmDebuggerLogic {
       self.event.trigger('newTrace', [])
     })
 
-    self.debugger.event.register('callTreeReady', function () {
+    self.debugger.callTree.event.register('callTreeReady', function () {
       if (self.debugger.callTree.reducedTrace.length) {
         return self.event.trigger('newCallTree', [])
       }
diff --git a/remix-debug/src/debugger/debugger.js b/remix-debug/src/debugger/debugger.js
index 0d9ede06de..56b911b844 100644
--- a/remix-debug/src/debugger/debugger.js
+++ b/remix-debug/src/debugger/debugger.js
@@ -69,34 +69,41 @@ Debugger.prototype.updateWeb3 = function (web3) {
 }
 
 Debugger.prototype.debug = function (blockNumber, txNumber, tx, loadingCb) {
-  const self = this
   let web3 = this.debugger.web3
 
-  if (this.debugger.traceManager.isLoading) {
-    return
-  }
+  return new Promise((resolve, reject) => {
+    if (this.debugger.traceManager.isLoading) {
+      return resolve()
+    }
 
-  if (tx) {
-    if (!tx.to) {
-      tx.to = traceHelper.contractCreationToken('0')
+    if (tx) {
+      if (!tx.to) {
+        tx.to = traceHelper.contractCreationToken('0')
+      }
+      this.debugTx(tx, loadingCb)
+      return resolve()
     }
-    return self.debugTx(tx, loadingCb)
-  }
-
-  try {
-    if (txNumber.indexOf('0x') !== -1) {
-      return web3.eth.getTransaction(txNumber, function (_error, result) {
-        let tx = result
-        self.debugTx(tx, loadingCb)
+
+    try {
+      if (txNumber.indexOf('0x') !== -1) {
+        return web3.eth.getTransaction(txNumber, (_error, tx) => {
+          if (_error) return reject(_error)
+          if (!tx) return reject('cannot find transaction ' + txNumber)
+          this.debugTx(tx, loadingCb)
+          return resolve()
+        })
+      }
+      web3.eth.getTransactionFromBlock(blockNumber, txNumber, (_error, tx) => {
+        if (_error) return reject(_error)
+        if (!tx) return reject('cannot find transaction ' + blockNumber + ' ' + txNumber)
+        this.debugTx(tx, loadingCb)
+        return resolve()
       })
+    } catch (e) {
+      console.error(e.message)
+      return reject(e.message)
     }
-    web3.eth.getTransactionFromBlock(blockNumber, txNumber, function (_error, result) {
-      let tx = result
-      self.debugTx(tx, loadingCb)
-    })
-  } catch (e) {
-    console.error(e.message)
-  }
+  })
 }
 
 Debugger.prototype.debugTx = function (tx, loadingCb) {
@@ -115,7 +122,7 @@ Debugger.prototype.debugTx = function (tx, loadingCb) {
   this.vmDebuggerLogic.start()
 
   this.step_manager.event.register('stepChanged', this, function (stepIndex) {
-    if (!stepIndex) {
+    if (typeof stepIndex !== 'number' || stepIndex >= self.step_manager.traceLength) {
       return self.event.trigger('endDebug')
     }