diff --git a/remix-debug/src/cmdline/contextManager.js b/remix-debug/src/cmdline/contextManager.js
index 82e165df34..0785724588 100644
--- a/remix-debug/src/cmdline/contextManager.js
+++ b/remix-debug/src/cmdline/contextManager.js
@@ -33,7 +33,7 @@ class ContextManager {
     this.event.trigger('providerAdded', [type])
   }
 
-  switchProvider (type) {
+  switchProvider (type, cb) {
     var self = this
     this.web3Providers.get(type, function (error, obj) {
       if (error) {
@@ -48,6 +48,7 @@ class ContextManager {
             self.web3 = (!webDebugNode ? obj : webDebugNode)
           }
           self.event.trigger('providerChanged', [type, self.web3])
+          if (cb) return cb();
         })
         self.event.trigger('providerChanged', [type, self.web3])
       }
diff --git a/remix-debug/src/cmdline/index.js b/remix-debug/src/cmdline/index.js
index 89baf560cb..94a1d22ab0 100644
--- a/remix-debug/src/cmdline/index.js
+++ b/remix-debug/src/cmdline/index.js
@@ -20,7 +20,7 @@ class CmdLine {
     this.compilation.lastCompilationResult = compilationResult
   }
 
-  initDebugger () {
+  initDebugger (cb) {
     const self = this
     this.contextManager = new ContextManager()
 
@@ -36,7 +36,7 @@ class CmdLine {
     this.contextManager.initProviders()
 
     this.contextManager.addProvider('debugger_web3', this.web3)
-    this.contextManager.switchProvider('debugger_web3')
+    this.contextManager.switchProvider('debugger_web3', cb)
   }
 
   getSource() {
@@ -44,7 +44,7 @@ class CmdLine {
 
     let lineColumnPos = this.lineColumnPos
 
-    if (!lineColumnPos || !lineColumnPos.start) return;
+    if (!lineColumnPos || !lineColumnPos.start) return [];
 
     let content = self.compilation.lastCompilationResult.source.sources[this.filename].content.split("\n")
 
@@ -74,7 +74,7 @@ class CmdLine {
   }
 
   // TODO: is filename really necessary?
-  startDebug(txNumber, filename) {
+  startDebug(txNumber, filename, cb) {
     const self = this
     this.filename = filename
     this.debugger.debug(null, txNumber, null, () => {
@@ -96,6 +96,7 @@ class CmdLine {
         self.events.emit("locals", data)
       });
 
+      cb()
     })
   }
 
diff --git a/remix-lib/src/trace/traceManager.js b/remix-lib/src/trace/traceManager.js
index 98785c54e4..90662b1132 100644
--- a/remix-lib/src/trace/traceManager.js
+++ b/remix-lib/src/trace/traceManager.js
@@ -120,7 +120,7 @@ TraceManager.prototype.getStackAt = function (stepIndex, callback) {
     return callback(check, null)
   }
   var stack
-  if (this.trace[stepIndex].stack) { // there's always a stack
+  if (this.trace[stepIndex] && this.trace[stepIndex].stack) { // there's always a stack
     stack = this.trace[stepIndex].stack.slice(0)
     stack.reverse()
     callback(null, stack)