diff --git a/theme.py b/theme.py
index 80de1c30d..60e4e4cf2 100644
--- a/theme.py
+++ b/theme.py
@@ -54,6 +54,8 @@ def _copyThemeHelpFiles(baseDir: str, themeName: str,
                         systemLanguage: str) -> None:
     """Copies any theme specific help files from the welcome subdirectory
     """
+    if not systemLanguage:
+        systemLanguage = 'en'
     themeDir = baseDir + '/theme/' + themeName + '/welcome'
     if not os.path.isdir(themeDir):
         themeDir = baseDir + '/defaultwelcome'