diff --git a/wmn/common.py b/wmn/common.py
index 20df6c0..51ddf97 100644
--- a/wmn/common.py
+++ b/wmn/common.py
@@ -56,7 +56,7 @@ def config_path() -> pathlib.Path:
     path = pathlib.Path(path)
     path = path.absolute().resolve()
     if not path.exists():
-        raise RuntimeError("Cannot find config: " + path)
+        raise RuntimeError(f"Cannot find config: {path}")
     return path