diff --git a/src/app/debugger/debuggerUI/ButtonNavigator.js b/src/app/debugger/debuggerUI/ButtonNavigator.js
index 12c9e4fa54..5710dc1f53 100644
--- a/src/app/debugger/debuggerUI/ButtonNavigator.js
+++ b/src/app/debugger/debuggerUI/ButtonNavigator.js
@@ -88,8 +88,6 @@ function ButtonNavigator (_parent, _traceManager) {
   this.view
 }
 
-module.exports = ButtonNavigator
-
 ButtonNavigator.prototype.render = function () {
   var self = this
   var view = yo`<div class="${css.buttons}">
@@ -130,29 +128,43 @@ ButtonNavigator.prototype.reset = function () {
   resetWarning(this)
 }
 
-ButtonNavigator.prototype.stepChanged = function (step) {
+ButtonNavigator.prototype.stepChanged = function (stepState, jumpOutDisabled) {
+  if (stepState === 'invalid') {
+    // TODO: probably not necessary, already implicit done in the next steps
+    this.reset()
+    this.updateAll()
+    return
+  }
+
+  this.intoBackDisabled = (stepState === 'initial')
+  this.overBackDisabled = (stepState === 'initial')
+  this.jumpPreviousBreakpointDisabled = (stepState === 'initial')
+  this.jumpNextBreakpointDisabled = (stepState === 'end')
+  this.intoForwardDisabled = (stepState === 'end')
+  this.overForwardDisabled = (stepState === 'end')
+  this.jumpNextBreakpointDisabled = jumpOutDisabled
+
+  this.updateAll()
+}
+
+ButtonNavigator.prototype.old_stepChanged = function (step) {
+  var self = this
   this.intoBackDisabled = step <= 0
   this.overBackDisabled = step <= 0
-  if (!this.traceManager) {
-    this.intoForwardDisabled = true
-    this.overForwardDisabled = true
-  } else {
-    var self = this
-    this.traceManager.getLength(function (error, length) {
-      if (error) {
-        self.reset()
-        console.log(error)
-      } else {
-        self.jumpNextBreakpointDisabled = step >= length - 1
-        self.jumpPreviousBreakpointDisabled = step <= 0
-        self.intoForwardDisabled = step >= length - 1
-        self.overForwardDisabled = step >= length - 1
-        var stepOut = self.traceManager.findStepOut(step)
-        self.jumpOutDisabled = stepOut === step
-      }
-      self.updateAll()
-    })
-  }
+  this.traceManager.getLength(function (error, length) {
+    if (error) {
+      console.log(error)
+      self.reset()
+    } else {
+      self.jumpNextBreakpointDisabled = step >= length - 1
+      self.jumpPreviousBreakpointDisabled = step <= 0
+      self.intoForwardDisabled = step >= length - 1
+      self.overForwardDisabled = step >= length - 1
+      var stepOut = self.traceManager.findStepOut(step)
+      self.jumpOutDisabled = stepOut === step
+    }
+    self.updateAll()
+  })
   this.updateAll()
 }
 
diff --git a/src/app/debugger/debuggerUI/Slider.js b/src/app/debugger/debuggerUI/Slider.js
index b3f84c7fce..3ca7eb8ffc 100644
--- a/src/app/debugger/debuggerUI/Slider.js
+++ b/src/app/debugger/debuggerUI/Slider.js
@@ -63,7 +63,7 @@ class Slider {
     if (value === this.previousValue) return
     this.previousValue = value
 
-    this.event.trigger('moved', [value])
+    this.event.trigger('sliderMoved', [value])
   }
 
   setValue (value) {
diff --git a/src/app/debugger/debuggerUI/StepManager.js b/src/app/debugger/debuggerUI/StepManager.js
index 7e223e1e7a..ed8edafb68 100644
--- a/src/app/debugger/debuggerUI/StepManager.js
+++ b/src/app/debugger/debuggerUI/StepManager.js
@@ -29,7 +29,7 @@ function StepManager (_parent, _traceManager) {
   this.slider = new Slider((step) => {
     return this.solidityMode ? this.resolveToReducedTrace(step, 0) : step
   })
-  this.slider.event.register('moved', this, function (step) {
+  this.slider.event.register('sliderMoved', this, function (step) {
     self.sliderMoved(step)
   })
 
@@ -197,8 +197,25 @@ StepManager.prototype.jumpOut = function () {
 }
 
 StepManager.prototype.changeState = function (step) {
+  const self = this
   this.currentStepIndex = step
-  this.buttonNavigator.stepChanged(step)
+
+  this.traceManager.getLength(function (error, length) {
+    let stepState = 'valid'
+
+    if (error) {
+      stepState = 'invalid'
+    } else if (step <= 0) {
+      stepState = 'initial'
+    } else if (step >= length - 1) {
+      stepState = 'end'
+    }
+
+    let jumpOutDisabled = (step === self.traceManager.findStepOut(step))
+
+    self.buttonNavigator.stepChanged(stepState, jumpOutDisabled)
+  })
+
   this.event.trigger('stepChanged', [step])
 }