diff --git a/etg/app.py b/etg/app.py
index bee9a137..77d5c6e2 100644
--- a/etg/app.py
+++ b/etg/app.py
@@ -522,7 +522,7 @@ def run():
                         except ValueError as ex:
                             target = wx.LogStderr()
                             orig = wx.Log.SetActiveTarget(target)
-                            wx.LogError(f"Unable to set default locale: '{ex}'")
+                            wx.LogError("Unable to set default locale: '{}'".format(ex))
                             wx.Log.SetActiveTarget(orig)
                     """),