diff --git a/docs/_ext/linkcode_res.py b/docs/_ext/linkcode_res.py
index 9b6f427d4..923925293 100644
--- a/docs/_ext/linkcode_res.py
+++ b/docs/_ext/linkcode_res.py
@@ -94,7 +94,7 @@ def linkcode_resolve(domain, info):
     fn = os.path.relpath(fn, start=os.path.dirname(cryptography.__file__))
 
     if lineno:
-        linespec = "#L%d-L%d" % (lineno, lineno + len(source) - 1)
+        linespec = f"#L{lineno}-L{lineno + len(source) - 1}"
     else:
         linespec = ""