diff --git a/Lib/collections/__init__.py b/Lib/collections/__init__.py
index 20f1e728733fec6..5dbcac19e7a9272 100644
--- a/Lib/collections/__init__.py
+++ b/Lib/collections/__init__.py
@@ -553,6 +553,9 @@ class Counter(dict):
     or multiset.  Elements are stored as dictionary keys and their counts
     are stored as dictionary values.
 
+    When constructed from a Mapping or Counter, the original object's
+    values will be used as the initial counts.
+
     >>> c = Counter('abcdeabcdabcaba')  # count elements from a string
 
     >>> c.most_common(3)                # three most common elements