diff --git a/fsl/utils/dialog.py b/fsl/utils/dialog.py
index 481670e731679acdfbacaf7a9f90fbea2b1aefa7..ccfa09f6e057e6c158a4885b3f5b91b6ec6728cf 100644
--- a/fsl/utils/dialog.py
+++ b/fsl/utils/dialog.py
@@ -94,7 +94,7 @@ class SimpleMessageDialog(wx.Dialog):
         self.__sizer.Add(self.__message,
                          border=25,
                          proportion=1,
-                         flag=wx.CENTRE | wx.ALL)
+                         flag=wx.EXPAND | wx.CENTRE | wx.ALL)
 
         self.SetTransparent(240)
         self.SetBackgroundColour((225, 225, 200))