diff --git a/Lib/test/test_codecs.py b/Lib/test/test_codecs.py
index acf9f64..1fa9ee0 100644
--- a/Lib/test/test_codecs.py
+++ b/Lib/test/test_codecs.py
@@ -1586,6 +1586,10 @@
             codecs.charmap_decode, b"\x00\x01\x02", "strict", "ab"
         )
 
+        self.assertRaises(UnicodeDecodeError,
+            codecs.charmap_decode, b"\x00\x01\x02", "strict", "ab\ufffe"
+        )
+
         self.assertEqual(
             codecs.charmap_decode(b"\x00\x01\x02", "replace", "ab"),
             ("ab\ufffd", 3)
@@ -1642,6 +1646,17 @@
                                    {0: 'a', 1: 'b'}
         )
 
+        self.assertRaises(UnicodeDecodeError,
+            codecs.charmap_decode, b"\x00\x01\x02", "strict",
+                                   {0: 'a', 1: 'b', 2: None}
+        )
+
+        # Issue #14850
+        self.assertRaises(UnicodeDecodeError,
+            codecs.charmap_decode, b"\x00\x01\x02", "strict",
+                                   {0: 'a', 1: 'b', 2: '\ufffe'}
+        )
+
         self.assertEqual(
             codecs.charmap_decode(b"\x00\x01\x02", "replace",
                                   {0: 'a', 1: 'b'}),
@@ -1654,6 +1669,13 @@
             ("ab\ufffd", 3)
         )
 
+        # Issue #14850
+        self.assertEqual(
+            codecs.charmap_decode(b"\x00\x01\x02", "replace",
+                                  {0: 'a', 1: 'b', 2: '\ufffe'}),
+            ("ab\ufffd", 3)
+        )
+
         self.assertEqual(
             codecs.charmap_decode(b"\x00\x01\x02", "ignore",
                                   {0: 'a', 1: 'b'}),
@@ -1666,6 +1688,13 @@
             ("ab", 3)
         )
 
+        # Issue #14850
+        self.assertEqual(
+            codecs.charmap_decode(b"\x00\x01\x02", "ignore",
+                                  {0: 'a', 1: 'b', 2: '\ufffe'}),
+            ("ab", 3)
+        )
+
         allbytes = bytes(range(256))
         self.assertEqual(
             codecs.charmap_decode(allbytes, "ignore", {}),
@@ -1700,6 +1729,11 @@
                                    {0: a, 1: b},
         )
 
+        self.assertRaises(UnicodeDecodeError,
+            codecs.charmap_decode, b"\x00\x01\x02", "strict",
+                                   {0: a, 1: b, 2: 0xFFFE},
+        )
+
         self.assertEqual(
             codecs.charmap_decode(b"\x00\x01\x02", "replace",
                                   {0: a, 1: b}),
@@ -1707,11 +1741,23 @@
         )
 
         self.assertEqual(
+            codecs.charmap_decode(b"\x00\x01\x02", "replace",
+                                  {0: a, 1: b, 2: 0xFFFE}),
+            ("ab\ufffd", 3)
+        )
+
+        self.assertEqual(
             codecs.charmap_decode(b"\x00\x01\x02", "ignore",
                                   {0: a, 1: b}),
             ("ab", 3)
         )
 
+        self.assertEqual(
+            codecs.charmap_decode(b"\x00\x01\x02", "ignore",
+                                  {0: a, 1: b, 2: 0xFFFE}),
+            ("ab", 3)
+        )
+
 
 class WithStmtTest(unittest.TestCase):
     def test_encodedfile(self):
diff --git a/Misc/NEWS b/Misc/NEWS
index 150f7fc..45c0598 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,9 @@
 Core and Builtins
 -----------------
 
+- Issue #14850: Now a chamap decoder treates U+FFFE as "undefined mapping"
+  in any mapping, not only in a string.
+
 - Issue #11461: Fix the incremental UTF-16 decoder. Original patch by
   Amaury Forgeot d'Arc.
 
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 7f86bfd..e1df874 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -5245,15 +5245,18 @@
                 if (PyErr_ExceptionMatches(PyExc_LookupError)) {
                     /* No mapping found means: mapping is undefined. */
                     PyErr_Clear();
-                    x = Py_None;
-                    Py_INCREF(x);
+                    goto Undefined;
                 } else
                     goto onError;
             }
 
             /* Apply mapping */
+            if (x == Py_None)
+                goto Undefined;
             if (PyLong_Check(x)) {
                 long value = PyLong_AS_LONG(x);
+                if (value == 0xFFFE)
+                    goto Undefined;
                 if (value < 0 || value > 0x10FFFF) {
                     PyErr_SetString(PyExc_TypeError,
                                     "character mapping must be in range(0x110000)");
@@ -5286,29 +5289,16 @@
 #endif
                 *p++ = (Py_UNICODE)value;
             }
-            else if (x == Py_None) {
-                /* undefined mapping */
-                outpos = p-PyUnicode_AS_UNICODE(v);
-                startinpos = s-starts;
-                endinpos = startinpos+1;
-                if (unicode_decode_call_errorhandler(
-                        errors, &errorHandler,
-                        "charmap", "character maps to <undefined>",
-                        &starts, &e, &startinpos, &endinpos, &exc, &s,
-                        &v, &outpos, &p)) {
-                    Py_DECREF(x);
-                    goto onError;
-                }
-                Py_DECREF(x);
-                continue;
-            }
             else if (PyUnicode_Check(x)) {
                 Py_ssize_t targetsize = PyUnicode_GET_SIZE(x);
 
-                if (targetsize == 1)
+                if (targetsize == 1) {
                     /* 1-1 mapping */
-                    *p++ = *PyUnicode_AS_UNICODE(x);
-
+                    Py_UNICODE value = *PyUnicode_AS_UNICODE(x);
+                    if (value == 0xFFFE)
+                        goto Undefined;
+                    *p++ = value;
+                }
                 else if (targetsize > 1) {
                     /* 1-n mapping */
                     if (targetsize > extrachars) {
@@ -5342,6 +5332,20 @@
             }
             Py_DECREF(x);
             ++s;
+            continue;
+Undefined:
+            /* undefined mapping */
+            Py_XDECREF(x);
+            outpos = p-PyUnicode_AS_UNICODE(v);
+            startinpos = s-starts;
+            endinpos = startinpos+1;
+            if (unicode_decode_call_errorhandler(
+                    errors, &errorHandler,
+                    "charmap", "character maps to <undefined>",
+                    &starts, &e, &startinpos, &endinpos, &exc, &s,
+                    &v, &outpos, &p)) {
+                goto onError;
+            }
         }
     }
     if (p - PyUnicode_AS_UNICODE(v) < PyUnicode_GET_SIZE(v))