diff --git a/pre_commit_hooks/check_docstring_first.py b/pre_commit_hooks/check_docstring_first.py
index cdf7b4c..3fc0c98 100644
--- a/pre_commit_hooks/check_docstring_first.py
+++ b/pre_commit_hooks/check_docstring_first.py
@@ -18,7 +18,7 @@ def _push_code(seen_code: io.StringIO, tok_type: int, text: str):
         return
     seen_code.write(text)
     if text and not text.isspace():
-        seen_code.write(" ")
+        seen_code.write(' ')
 
 
 def check_docstring_first(src: bytes, filename: str = '<unknown>') -> int: