diff --git a/Lib/json/decoder.py b/Lib/json/decoder.py
index c5d9ae2d0d5d04..17caf7001b41a5 100644
--- a/Lib/json/decoder.py
+++ b/Lib/json/decoder.py
@@ -203,6 +203,8 @@ def JSONObject(s_and_end, strict, scan_once, object_hook, object_pairs_hook,
         end = _w(s, end).end()
         nextchar = s[end:end + 1]
         end += 1
+        if nextchar == '}':
+            raise JSONDecodeError("Trailing commas are not allowed in JSON objects.")
         if nextchar != '"':
             raise JSONDecodeError(
                 "Expecting property name enclosed in double quotes", s, end - 1)