diff --git a/openlp/core/utils/__init__.py b/openlp/core/utils/__init__.py
index 086c69c79..69187ed74 100644
--- a/openlp/core/utils/__init__.py
+++ b/openlp/core/utils/__init__.py
@@ -529,7 +529,7 @@ def get_natural_key(string):
     key = [int(part) if part.isdigit() else get_locale_key(part) for part in key]
     # Python 3 does not support comparison of different types anymore. So make sure, that we do not compare str
     # and int.
-    if string[0].isdigit():
+    if string and string[0].isdigit():
         return [b''] + key
     return key