only fast-path fromkeys() when the constructor returns a empty dict (closes #16345)
diff --git a/Misc/NEWS b/Misc/NEWS
index 434f221..bd6cd80 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,9 @@
 Core and Builtins
 -----------------
 
+- Issue #16345: Fix an infinite loop when ``fromkeys`` on a dict subclass
+  recieved a nonempty dict from the constructor.
+
 - Issue #16197: Update winreg docstrings and documentation to match code.
   Patch by Zachary Ware.