diff --git a/api/py/ai/chronon/group_by.py b/api/py/ai/chronon/group_by.py
index 18194f60f4..3b95bbba08 100644
--- a/api/py/ai/chronon/group_by.py
+++ b/api/py/ai/chronon/group_by.py
@@ -61,7 +61,7 @@ class Operation:
     APPROX_UNIQUE_COUNT = ttypes.Operation.APPROX_UNIQUE_COUNT
     # refer to the chart here to tune your sketch size with lgK
     # default is 8
-    # https://github.com/apache/incubator-datasketches-java/blob/main/src/main/java/org/apache/datasketches/cpc/CpcSketch.java#L180
+    # https://github.com/apache/incubator-datasketches-java/blob/master/src/main/java/org/apache/datasketches/cpc/CpcSketch.java#L180
     APPROX_UNIQUE_COUNT_LGK = collector(ttypes.Operation.APPROX_UNIQUE_COUNT)
     UNIQUE_COUNT = ttypes.Operation.UNIQUE_COUNT
     COUNT = ttypes.Operation.COUNT