diff --git a/blurb/blurb.py b/blurb/blurb.py
index cd975ba..04448d7 100755
--- a/blurb/blurb.py
+++ b/blurb/blurb.py
@@ -483,6 +483,8 @@ def parse(self, text, *, metadata=None, filename="input"):
         line_number = None
 
         def throw(s):
+            nonlocal filename
+            nonlocal line_number
             raise BlurbError(f("Error in {filename}:{line_number}:\n{s}"))
 
         def finish_entry():