diff --git a/km3io/tools.py b/km3io/tools.py
index 967d28c08ee32981ed8224adbf1920633518e47d..67d2c7415e2666702fcff5b72892670d43cd1195 100644
--- a/km3io/tools.py
+++ b/km3io/tools.py
@@ -221,7 +221,7 @@ def count_nested(Array, axis=0):
 
 
 def get_multiplicity(tracks, rec_stages):
-    """tracks selection based on specific reconstruction stages (for multiplicity
+    """Tracks selection based on specific reconstruction stages (for multiplicity
     calculations).
 
     Parameters