diff --git a/invesalius/data/slice_.py b/invesalius/data/slice_.py
index c853e7a..a3abefa 100644
--- a/invesalius/data/slice_.py
+++ b/invesalius/data/slice_.py
@@ -126,6 +126,16 @@ class Slice(object):
         ps.Publisher().subscribe(self.OnRemoveMasks, 'Remove masks')
         ps.Publisher().subscribe(self.OnDuplicateMasks, 'Duplicate masks')
 
+    def GetMaxSliceNumber(self, orientation):
+        shape = self.matrix.shape
+
+        if orientation == 'AXIAL':
+            return shape[0]
+        elif orientation == 'CORONAL':
+            return shape[1]
+        elif orientation == 'SAGITAL':
+            return shape[2]
+
     def OnRemoveMasks(self, pubsub_evt):
         selected_items = pubsub_evt.data
         proj = Project()
diff --git a/invesalius/data/viewer_slice.py b/invesalius/data/viewer_slice.py
index 6a7b0dd..8363e5b 100755
--- a/invesalius/data/viewer_slice.py
+++ b/invesalius/data/viewer_slice.py
@@ -1330,7 +1330,7 @@ class Viewer(wx.Panel):
         pos = self.scroll.GetThumbPosition()
 
         min = 0
-        max = self.actor.GetSliceNumberMax()
+        max = self.slice_.GetMaxSliceNumber(self.orientation)
 
         if (evt.GetKeyCode() == wx.WXK_UP and pos > min):
             self.OnScrollForward()
@@ -1359,7 +1359,7 @@ class Viewer(wx.Panel):
     
     def OnScrollBackward(self, evt=None, obj=None):
         pos = self.scroll.GetThumbPosition()
-        max = self.actor.GetSliceNumberMax()
+        max = self.slice_.GetMaxSliceNumber(self.orientation)
         
         if(pos < max):
             pos = pos + 1
--
libgit2 0.21.2