diff --git a/source/fab/steps/grab/svn.py b/source/fab/steps/grab/svn.py
index dd8b4894..59cb6618 100644
--- a/source/fab/steps/grab/svn.py
+++ b/source/fab/steps/grab/svn.py
@@ -12,7 +12,8 @@
 from fab.tools import run_command
 
 
-def split_repo_url(url: str, revision: str = None) -> Tuple[str, Optional[str]]:
+def split_repo_url(url: str,
+                   revision: Optional[str] = None) -> Tuple[str, Optional[str]]:
     """
     Separates revision from a repository URL.