diff --git a/bin/diann_convert.py b/bin/diann_convert.py
index ead4d522..498a00f5 100755
--- a/bin/diann_convert.py
+++ b/bin/diann_convert.py
@@ -1254,6 +1254,10 @@ def calculate_coverage(ref_sequence: str, sequences: Set[str]):
     1.0
     >>> calculate_coverage("WATERGLASS", {"WAT", "TER"})
     0.5
+    >>> calculate_coverage("WATER", {"WAT", "TER"})
+    1.0
+    >>> calculate_coverage("WATERGLASS", {"WAT", "TER"})
+    0.5
     """
     starts = []
     lengths = []