diff --git a/bin/diann_convert.py b/bin/diann_convert.py
index bb4a41c6..a30e91fc 100755
--- a/bin/diann_convert.py
+++ b/bin/diann_convert.py
@@ -1234,7 +1234,7 @@ def calculate_coverage(ref_sequence: str, sequences: Set[str]):
 
     Examples:
     >>> calculate_coverage("WATEROVERTHEDUCKSBACK", {"WATER", "DUCK"})
-    0.45
+    0.42857142857142855
     >>> calculate_coverage("DUCKDUCKDUCK", {"DUCK"})
     1.0
     >>> calculate_coverage("WATEROVERTHEDUCK", {"DUCK"})
@@ -1243,14 +1243,6 @@ 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
-    >>> calculate_coverage("WATER", {"WAT", "TER"})
-    1.0
-    >>> calculate_coverage("WATERGLASS", {"WAT", "TER"})
-    0.5
     """
     starts = []
     lengths = []
@@ -1267,7 +1259,7 @@ def calculate_coverage(ref_sequence: str, sequences: Set[str]):
     # merge overlapping intervals
     merged_starts: list = []
     merged_lengths: list = []
-    for start, length in zip(*sorted(zip(starts, lengths))):
+    for start, length in sorted(zip(starts, lengths)):
         if merged_starts and merged_starts[-1] + merged_lengths[-1] >= start:
             merged_lengths[-1] = max(merged_starts[-1] + merged_lengths[-1], start + length) - merged_starts[-1]
         else: