diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index e7bbd80..02b4823 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -1419,34 +1419,30 @@ PyObject *PyUnicode_FromEncodedObject(register PyObject *obj,
     return v;
 }
 
-/* Convert encoding to lower case and replace '_' with '-' in order to
-   catch e.g. UTF_8. Return 0 on error (encoding is longer than lower_len-1),
-   1 on success. */
+/* Convert encoding to lower case and skip characters different than a-z and
+   0-9. Return 0 on error (encoding is longer than lower_len-1), 1 on success.
+ */
 static int
 normalize_encoding(const char *encoding,
                    char *lower,
                    size_t lower_len)
 {
     const char *e;
-    char *l;
+    char *l, c;
     char *l_end;
 
     e = encoding;
     l = lower;
     l_end = &lower[lower_len - 1];
-    while (*e) {
+    for (; *e; e++) {
         if (l == l_end)
             return 0;
-        if (Py_ISUPPER(*e)) {
-            *l++ = Py_TOLOWER(*e++);
-        }
-        else if (*e == '_') {
-            *l++ = '-';
-            e++;
-        }
-        else {
-            *l++ = *e++;
-        }
+        c = *e;
+        if (('a' <= c && c <= 'z') || ('0' <= c && c <= '9'))
+            *l++ = c;
+        else if ('A' <= c && c <= 'Z')
+            *l++ = c + ('a' - 'A');
+        /* else: ignore the character */
     }
     *l = '\0';
     return 1;
@@ -1466,10 +1462,10 @@ PyObject *PyUnicode_Decode(const char *s,
 
     /* Shortcuts for common default encodings */
     if (normalize_encoding(encoding, lower, sizeof(lower))) {
-        if (strcmp(lower, "utf-8") == 0)
+        if (strcmp(lower, "utf8") == 0)
             return PyUnicode_DecodeUTF8(s, size, errors);
-        else if ((strcmp(lower, "latin-1") == 0) ||
-                 (strcmp(lower, "iso-8859-1") == 0))
+        else if ((strcmp(lower, "latin1") == 0) ||
+                 (strcmp(lower, "iso88591") == 0))
             return PyUnicode_DecodeLatin1(s, size, errors);
 #if defined(MS_WINDOWS) && defined(HAVE_USABLE_WCHAR_T)
         else if (strcmp(lower, "mbcs") == 0)
@@ -1477,9 +1473,9 @@ PyObject *PyUnicode_Decode(const char *s,
 #endif
         else if (strcmp(lower, "ascii") == 0)
             return PyUnicode_DecodeASCII(s, size, errors);
-        else if (strcmp(lower, "utf-16") == 0)
+        else if (strcmp(lower, "utf16") == 0)
             return PyUnicode_DecodeUTF16(s, size, errors, 0);
-        else if (strcmp(lower, "utf-32") == 0)
+        else if (strcmp(lower, "utf32") == 0)
             return PyUnicode_DecodeUTF32(s, size, errors, 0);
     }
 
@@ -1674,12 +1670,12 @@ PyObject *PyUnicode_AsEncodedString(PyObject *unicode,
 
     /* Shortcuts for common default encodings */
     if (normalize_encoding(encoding, lower, sizeof(lower))) {
-        if (strcmp(lower, "utf-8") == 0)
+        if (strcmp(lower, "utf8") == 0)
             return PyUnicode_EncodeUTF8(PyUnicode_AS_UNICODE(unicode),
                                         PyUnicode_GET_SIZE(unicode),
                                         errors);
-        else if ((strcmp(lower, "latin-1") == 0) ||
-                 (strcmp(lower, "iso-8859-1") == 0))
+        else if ((strcmp(lower, "latin1") == 0) ||
+                 (strcmp(lower, "iso88591") == 0))
             return PyUnicode_EncodeLatin1(PyUnicode_AS_UNICODE(unicode),
                                           PyUnicode_GET_SIZE(unicode),
                                           errors);