diff --git a/.gitignore b/.gitignore
index 6b5141314..0d5943d5a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -17,6 +17,7 @@ dist/
 mitmproxy/contrib/kaitaistruct/*.ksy
 .pytest_cache
 __pycache__
+.hypothesis/
 
 # UI
 
diff --git a/mitmproxy/net/http/http1/read.py b/mitmproxy/net/http/http1/read.py
index fbf5da2b7..0fc03f1b6 100644
--- a/mitmproxy/net/http/http1/read.py
+++ b/mitmproxy/net/http/http1/read.py
@@ -220,8 +220,8 @@ def expected_http_body_size(
             if size < 0:
                 raise ValueError()
             return size
-        except ValueError:
-            raise exceptions.HttpSyntaxException("Unparseable Content Length")
+        except ValueError as e:
+            raise exceptions.HttpSyntaxException("Unparseable Content Length") from e
     if not response:
         return 0
     return -1