diff --git a/lib/matplotlib/backends/backend_wx.py b/lib/matplotlib/backends/backend_wx.py
index 0ae70707ac0d..32093cfe3b2e 100644
--- a/lib/matplotlib/backends/backend_wx.py
+++ b/lib/matplotlib/backends/backend_wx.py
@@ -1165,6 +1165,7 @@ def __init__(self, toolmanager, parent=None, style=wx.TB_BOTTOM):
         if parent is None:
             parent = toolmanager.canvas.GetParent()
         ToolContainerBase.__init__(self, toolmanager)
+        self._icon_extension = '.svg' # wx backend wants 'svg' tool icons
         wx.ToolBar.__init__(self, parent, -1, style=style)
         self._space = self.AddStretchableSpace()
         self._label_text = wx.StaticText(self, style=wx.ALIGN_RIGHT)