diff --git a/ingest/parsers.py b/ingest/parsers.py
index 3cd419d..9789750 100644
--- a/ingest/parsers.py
+++ b/ingest/parsers.py
@@ -184,7 +184,8 @@ class StreamingEnvelopeParser:
                 should_be_empty = io.BytesIO()
                 self.remainder, self.at_eof = readuntil(
                     self.input_stream, self.remainder, NewlineFinder(), should_be_empty, self.chunk_size)
-                if should_be_empty.getvalue() != b"":
+                should_be_empty_value = should_be_empty.getvalue()
+                if should_be_empty_value != b"":
                     raise ParseError("Item with explicit length not terminated by newline/EOF")
 
             yield item_headers, item_output_stream