diff --git a/Lib/json/scanner.py b/Lib/json/scanner.py
index c451ebab5842555..7a61cfc2d24dceb 100644
--- a/Lib/json/scanner.py
+++ b/Lib/json/scanner.py
@@ -68,6 +68,6 @@ def scan_once(string, idx):
         finally:
             memo.clear()
 
-    return _scan_once
+    return scan_once
 
 make_scanner = c_make_scanner or py_make_scanner
diff --git a/Lib/test/test_json/test_decode.py b/Lib/test/test_json/test_decode.py
index d84ef7da24463bd..fdb9e62124ece1f 100644
--- a/Lib/test/test_json/test_decode.py
+++ b/Lib/test/test_json/test_decode.py
@@ -58,7 +58,9 @@ def check_keys_reuse(self, source, loads):
     def test_keys_reuse(self):
         s = '[{"a_key": 1, "b_\xe9": 2}, {"a_key": 3, "b_\xe9": 4}]'
         self.check_keys_reuse(s, self.loads)
-        self.check_keys_reuse(s, self.json.decoder.JSONDecoder().decode)
+        decoder = self.json.decoder.JSONDecoder()
+        self.check_keys_reuse(s, decoder.decode)
+        self.assertFalse(decoder.memo)
 
     def test_extra_data(self):
         s = '[1, 2, 3]5'
diff --git a/Misc/NEWS.d/next/Library/2018-05-22-13-05-12.bpo-30877.JZEGjI.rst b/Misc/NEWS.d/next/Library/2018-05-22-13-05-12.bpo-30877.JZEGjI.rst
new file mode 100644
index 000000000000000..4be0fae4ecb68e2
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2018-05-22-13-05-12.bpo-30877.JZEGjI.rst
@@ -0,0 +1,3 @@
+Fixed a bug in the Python implementation of the JSON decoder that prevented
+the cache of parsed strings from clearing after finishing the decoding.
+Based on patch by c-fos.