diff --git a/python/mocpy/moc/moc.py b/python/mocpy/moc/moc.py
index 5d1335c7..defb4058 100644
--- a/python/mocpy/moc/moc.py
+++ b/python/mocpy/moc/moc.py
@@ -71,6 +71,7 @@ class MOC(AbstractMOC):
     """
 
     # Maximum order (or depth) of a MOC
+    # (do not remove since it may be used externally).
     MAX_ORDER = np.uint8(29)
 
     __create_key = object()
diff --git a/python/mocpy/tmoc/tmoc.py b/python/mocpy/tmoc/tmoc.py
index a32c1a94..9234b19a 100644
--- a/python/mocpy/tmoc/tmoc.py
+++ b/python/mocpy/tmoc/tmoc.py
@@ -64,6 +64,7 @@ class TimeMOC(AbstractMOC):
     """Multi-order time coverage class. Experimental."""
 
     # Maximum order of TimeMOCs
+    # (do not remove since it may be used externally).
     MAX_ORDER = np.uint8(61)
     # Number of microseconds in a day
     DAY_MICRO_SEC = 86400000000.0