diff --git a/Lib/modulefinder.py b/Lib/modulefinder.py
index cd9906c..cc5ad19 100644
--- a/Lib/modulefinder.py
+++ b/Lib/modulefinder.py
@@ -17,12 +17,12 @@
     READ_MODE = "r"
 
 # XXX Clean up once str8's cstor matches bytes.
-LOAD_CONST = str8(chr(dis.opname.index('LOAD_CONST')))
-IMPORT_NAME = str8(chr(dis.opname.index('IMPORT_NAME')))
-STORE_NAME = str8(chr(dis.opname.index('STORE_NAME')))
-STORE_GLOBAL = str8(chr(dis.opname.index('STORE_GLOBAL')))
+LOAD_CONST = str8([dis.opname.index('LOAD_CONST')])
+IMPORT_NAME = str8([dis.opname.index('IMPORT_NAME')])
+STORE_NAME = str8([dis.opname.index('STORE_NAME')])
+STORE_GLOBAL = str8([dis.opname.index('STORE_GLOBAL')])
 STORE_OPS = [STORE_NAME, STORE_GLOBAL]
-HAVE_ARGUMENT = str8(chr(dis.HAVE_ARGUMENT))
+HAVE_ARGUMENT = str8([dis.HAVE_ARGUMENT])
 
 # Modulefinder does a good job at simulating Python's, but it can not
 # handle __path__ modifications packages make at runtime.  Therefore there
@@ -368,7 +368,7 @@
         consts = co.co_consts
         LOAD_LOAD_AND_IMPORT = LOAD_CONST + LOAD_CONST + IMPORT_NAME
         while code:
-            c = str8(chr(code[0]))
+            c = str8([code[0]])
             if c in STORE_OPS:
                 oparg, = unpack('<H', code[1:3])
                 yield "store", (names[oparg],)
diff --git a/Lib/pickletools.py b/Lib/pickletools.py
index 6b0fca7..b1337c4 100644
--- a/Lib/pickletools.py
+++ b/Lib/pickletools.py
@@ -1978,7 +1978,7 @@
 
 _dis_test = r"""
 >>> import pickle
->>> x = [1, 2, (3, 4), {str8('abc'): "def"}]
+>>> x = [1, 2, (3, 4), {str8(b'abc'): "def"}]
 >>> pkl = pickle.dumps(x, 0)
 >>> dis(pkl)
     0: (    MARK
diff --git a/Lib/struct.py b/Lib/struct.py
index 027caa2..10085b7 100644
--- a/Lib/struct.py
+++ b/Lib/struct.py
@@ -36,7 +36,7 @@
 class Struct(_Struct):
     def __init__(self, fmt):
         if isinstance(fmt, str):
-            fmt = str8(fmt)
+            fmt = str8(fmt, 'latin1')
         _Struct.__init__(self, fmt)
 
 _MAXCACHE = 100
diff --git a/Lib/test/test_builtin.py b/Lib/test/test_builtin.py
index b6b45ee..9670be0 100644
--- a/Lib/test/test_builtin.py
+++ b/Lib/test/test_builtin.py
@@ -580,7 +580,8 @@
         self.assertEqual(hash(1), hash(1))
         self.assertEqual(hash(1), hash(1.0))
         hash('spam')
-        self.assertEqual(hash('spam'), hash(str8('spam')))
+        self.assertEqual(hash('spam'), hash(str8(b'spam'))) # remove str8()
+                                                    # when b"" is immutable
         hash((0,1,2,3))
         def f(): pass
         self.assertRaises(TypeError, hash, [])
diff --git a/Lib/test/test_bytes.py b/Lib/test/test_bytes.py
index c7c6bd3..2a4b6d8 100644
--- a/Lib/test/test_bytes.py
+++ b/Lib/test/test_bytes.py
@@ -103,33 +103,33 @@
         self.failIf(b3 <= b2)
 
     def test_compare_to_str(self):
-        self.assertEqual(b"abc" == str8("abc"), True)
-        self.assertEqual(b"ab" != str8("abc"), True)
-        self.assertEqual(b"ab" <= str8("abc"), True)
-        self.assertEqual(b"ab" < str8("abc"), True)
-        self.assertEqual(b"abc" >= str8("ab"), True)
-        self.assertEqual(b"abc" > str8("ab"), True)
+        self.assertEqual(b"abc" == str8(b"abc"), True)
+        self.assertEqual(b"ab" != str8(b"abc"), True)
+        self.assertEqual(b"ab" <= str8(b"abc"), True)
+        self.assertEqual(b"ab" < str8(b"abc"), True)
+        self.assertEqual(b"abc" >= str8(b"ab"), True)
+        self.assertEqual(b"abc" > str8(b"ab"), True)
 
-        self.assertEqual(b"abc" != str8("abc"), False)
-        self.assertEqual(b"ab" == str8("abc"), False)
-        self.assertEqual(b"ab" > str8("abc"), False)
-        self.assertEqual(b"ab" >= str8("abc"), False)
-        self.assertEqual(b"abc" < str8("ab"), False)
-        self.assertEqual(b"abc" <= str8("ab"), False)
+        self.assertEqual(b"abc" != str8(b"abc"), False)
+        self.assertEqual(b"ab" == str8(b"abc"), False)
+        self.assertEqual(b"ab" > str8(b"abc"), False)
+        self.assertEqual(b"ab" >= str8(b"abc"), False)
+        self.assertEqual(b"abc" < str8(b"ab"), False)
+        self.assertEqual(b"abc" <= str8(b"ab"), False)
 
-        self.assertEqual(str8("abc") == b"abc", True)
-        self.assertEqual(str8("ab") != b"abc", True)
-        self.assertEqual(str8("ab") <= b"abc", True)
-        self.assertEqual(str8("ab") < b"abc", True)
-        self.assertEqual(str8("abc") >= b"ab", True)
-        self.assertEqual(str8("abc") > b"ab", True)
+        self.assertEqual(str8(b"abc") == b"abc", True)
+        self.assertEqual(str8(b"ab") != b"abc", True)
+        self.assertEqual(str8(b"ab") <= b"abc", True)
+        self.assertEqual(str8(b"ab") < b"abc", True)
+        self.assertEqual(str8(b"abc") >= b"ab", True)
+        self.assertEqual(str8(b"abc") > b"ab", True)
 
-        self.assertEqual(str8("abc") != b"abc", False)
-        self.assertEqual(str8("ab") == b"abc", False)
-        self.assertEqual(str8("ab") > b"abc", False)
-        self.assertEqual(str8("ab") >= b"abc", False)
-        self.assertEqual(str8("abc") < b"ab", False)
-        self.assertEqual(str8("abc") <= b"ab", False)
+        self.assertEqual(str8(b"abc") != b"abc", False)
+        self.assertEqual(str8(b"ab") == b"abc", False)
+        self.assertEqual(str8(b"ab") > b"abc", False)
+        self.assertEqual(str8(b"ab") >= b"abc", False)
+        self.assertEqual(str8(b"abc") < b"ab", False)
+        self.assertEqual(str8(b"abc") <= b"ab", False)
 
         # Byte comparisons with unicode should always fail!
         # Test this for all expected byte orders and Unicode character sizes
@@ -345,7 +345,7 @@
         self.assertEqual(b.decode("utf8", "ignore"), "Hello world\n")
 
     def test_from_buffer(self):
-        sample = str8("Hello world\n\x80\x81\xfe\xff")
+        sample = str8(b"Hello world\n\x80\x81\xfe\xff")
         buf = memoryview(sample)
         b = bytes(buf)
         self.assertEqual(b, bytes(sample))
@@ -367,8 +367,8 @@
         b1 = b"abc"
         b2 = b"def"
         self.assertEqual(b1 + b2, b"abcdef")
-        self.assertEqual(b1 + str8("def"), b"abcdef")
-        self.assertEqual(str8("def") + b1, b"defabc")
+        self.assertEqual(b1 + str8(b"def"), b"abcdef")
+        self.assertEqual(str8(b"def") + b1, b"defabc")
         self.assertRaises(TypeError, lambda: b1 + "def")
         self.assertRaises(TypeError, lambda: "abc" + b2)
 
@@ -391,7 +391,7 @@
         self.assertEqual(b, b"abcdef")
         self.assertEqual(b, b1)
         self.failUnless(b is b1)
-        b += str8("xyz")
+        b += str8(b"xyz")
         self.assertEqual(b, b"abcdefxyz")
         try:
             b += ""
diff --git a/Lib/test/test_codeccallbacks.py b/Lib/test/test_codeccallbacks.py
index eedd48a..0256eb6 100644
--- a/Lib/test/test_codeccallbacks.py
+++ b/Lib/test/test_codeccallbacks.py
@@ -181,7 +181,7 @@
         # mapped through the encoding again. This means, that
         # to be able to use e.g. the "replace" handler, the
         # charmap has to have a mapping for "?".
-        charmap = dict((ord(c), str8(2*c.upper())) for c in "abcdefgh")
+        charmap = dict((ord(c), str8(2*c.upper(), 'ascii')) for c in "abcdefgh")
         sin = "abc"
         sout = b"AABBCC"
         self.assertEquals(codecs.charmap_encode(sin, "strict", charmap)[0], sout)
@@ -189,7 +189,7 @@
         sin = "abcA"
         self.assertRaises(UnicodeError, codecs.charmap_encode, sin, "strict", charmap)
 
-        charmap[ord("?")] = str8("XYZ")
+        charmap[ord("?")] = str8(b"XYZ")
         sin = "abcDEF"
         sout = b"AABBCCXYZXYZXYZ"
         self.assertEquals(codecs.charmap_encode(sin, "replace", charmap)[0], sout)
@@ -309,7 +309,7 @@
         # check with one argument too much
         self.assertRaises(TypeError, exctype, *(args + ["too much"]))
         # check with one argument of the wrong type
-        wrongargs = [ "spam", str8("eggs"), b"spam", 42, 1.0, None ]
+        wrongargs = [ "spam", str8(b"eggs"), b"spam", 42, 1.0, None ]
         for i in range(len(args)):
             for wrongarg in wrongargs:
                 if type(wrongarg) is type(args[i]):
diff --git a/Lib/test/test_compile.py b/Lib/test/test_compile.py
index d6a51dd..1d54953 100644
--- a/Lib/test/test_compile.py
+++ b/Lib/test/test_compile.py
@@ -157,7 +157,7 @@
         s256 = "".join(["\n"] * 256 + ["spam"])
         co = compile(s256, 'fn', 'exec')
         self.assertEqual(co.co_firstlineno, 257)
-        self.assertEqual(co.co_lnotab, str8(''))
+        self.assertEqual(co.co_lnotab, str8())
 
     def test_literals_with_leading_zeroes(self):
         for arg in ["077787", "0xj", "0x.", "0e",  "090000000000000",
diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index 644593d..e826ff4 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -88,7 +88,7 @@
         self.assertEqual(f.tell(), 6)
         self.assertEqual(f.seek(-1, 1), 5)
         self.assertEqual(f.tell(), 5)
-        self.assertEqual(f.write(str8(" world\n\n\n")), 9)
+        self.assertEqual(f.write(str8(b" world\n\n\n")), 9)
         self.assertEqual(f.seek(0), 0)
         self.assertEqual(f.write(b"h"), 1)
         self.assertEqual(f.seek(-1, 2), 13)
diff --git a/Lib/test/test_locale.py b/Lib/test/test_locale.py
index 1bfb3b3..5fcba6f 100644
--- a/Lib/test/test_locale.py
+++ b/Lib/test/test_locale.py
@@ -82,7 +82,7 @@
 
 # Test BSD Rune locale's bug for isctype functions.
 def teststrop(s, method, output):
-    s = str8(s)
+    s = str8(s, 'latin1') # XXX
     if verbose:
         print("%s.%s() =? %s ..." % (repr(s), method, repr(output)), end=' ')
     result = getattr(s, method)()
diff --git a/Lib/test/test_struct.py b/Lib/test/test_struct.py
index 7942045..d2b5643 100644
--- a/Lib/test/test_struct.py
+++ b/Lib/test/test_struct.py
@@ -101,7 +101,7 @@
 simple_err(struct.unpack, 'iii', s)
 simple_err(struct.unpack, 'i', s)
 
-c = str8('a')
+c = str8(b'a')
 b = 1
 h = 255
 i = 65535
@@ -186,7 +186,7 @@
         if isinstance(arg, str):
             # Strings are returned as str8 since you can't know the encoding of
             # the string when packed.
-            arg = str8(arg)
+            arg = str8(arg, 'latin1')
         if rev != arg and not asy:
             raise TestFailed("unpack(%r, %r) -> (%r,) # expected (%r,)" % (
                 fmt, res, rev, arg))
@@ -428,14 +428,14 @@
 
 def test_p_code():
     for code, input, expected, expectedback in [
-            ('p','abc', '\x00', str8('')),
-            ('1p', 'abc', '\x00', str8('')),
-            ('2p', 'abc', '\x01a', str8('a')),
-            ('3p', 'abc', '\x02ab', str8('ab')),
-            ('4p', 'abc', '\x03abc', str8('abc')),
-            ('5p', 'abc', '\x03abc\x00', str8('abc')),
-            ('6p', 'abc', '\x03abc\x00\x00', str8('abc')),
-            ('1000p', 'x'*1000, '\xff' + 'x'*999, str8('x'*255))]:
+            ('p','abc', '\x00', str8()),
+            ('1p', 'abc', '\x00', str8()),
+            ('2p', 'abc', '\x01a', str8(b'a')),
+            ('3p', 'abc', '\x02ab', str8(b'ab')),
+            ('4p', 'abc', '\x03abc', str8(b'abc')),
+            ('5p', 'abc', '\x03abc\x00', str8(b'abc')),
+            ('6p', 'abc', '\x03abc\x00\x00', str8(b'abc')),
+            ('1000p', 'x'*1000, '\xff' + 'x'*999, str8(b'x'*255))]:
         expected = bytes(expected, "latin-1")
         got = struct.pack(code, input)
         if got != expected:
@@ -564,20 +564,24 @@
         if verbose:
             print("test_unpack_from using", cls.__name__)
         data = cls(test_string)
-        vereq(s.unpack_from(data), (str8('abcd'),))
-        vereq(s.unpack_from(data, 2), (str8('cd01'),))
-        vereq(s.unpack_from(data, 4), (str8('0123'),))
+        if not isinstance(data, (str8, bytes)):
+            bytes_data = str8(data, 'latin1')
+        else:
+            bytes_data = data
+        vereq(s.unpack_from(data), (str8(b'abcd'),))
+        vereq(s.unpack_from(data, 2), (str8(b'cd01'),))
+        vereq(s.unpack_from(data, 4), (str8(b'0123'),))
         for i in range(6):
-            vereq(s.unpack_from(data, i), (str8(data[i:i+4]),))
+            vereq(s.unpack_from(data, i), (bytes_data[i:i+4],))
         for i in range(6, len(test_string) + 1):
             simple_err(s.unpack_from, data, i)
     for cls in (str, str8, bytes): # XXX + memoryview
         data = cls(test_string)
-        vereq(struct.unpack_from(fmt, data), (str8('abcd'),))
-        vereq(struct.unpack_from(fmt, data, 2), (str8('cd01'),))
-        vereq(struct.unpack_from(fmt, data, 4), (str8('0123'),))
+        vereq(struct.unpack_from(fmt, data), (str8(b'abcd'),))
+        vereq(struct.unpack_from(fmt, data, 2), (str8(b'cd01'),))
+        vereq(struct.unpack_from(fmt, data, 4), (str8(b'0123'),))
         for i in range(6):
-            vereq(struct.unpack_from(fmt, data, i), (str8(data[i:i+4]),))
+            vereq(struct.unpack_from(fmt, data, i), (bytes_data[i:i+4],))
         for i in range(6, len(test_string) + 1):
             simple_err(struct.unpack_from, fmt, data, i)
 
diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
index ddf1876..8741830 100644
--- a/Lib/test/test_sys.py
+++ b/Lib/test/test_sys.py
@@ -300,7 +300,7 @@
 
     def test_intern(self):
         self.assertRaises(TypeError, sys.intern)
-        s = str8("never interned before")
+        s = str8(b"never interned before")
         self.assert_(sys.intern(s) is s)
         s2 = s.swapcase().swapcase()
         self.assert_(sys.intern(s2) is s)
@@ -314,7 +314,7 @@
             def __hash__(self):
                 return 123
 
-        self.assertRaises(TypeError, sys.intern, S("abc"))
+        self.assertRaises(TypeError, sys.intern, S(b"abc"))
 
         s = "never interned as unicode before"
         self.assert_(sys.intern(s) is s)
diff --git a/Lib/test/test_unicode.py b/Lib/test/test_unicode.py
index 9aad59a..4970845 100644
--- a/Lib/test/test_unicode.py
+++ b/Lib/test/test_unicode.py
@@ -203,8 +203,8 @@
         self.assertRaises(TypeError, 'replace'.replace, "r", 42)
 
     def test_str8_comparison(self):
-        self.assertEqual('abc' == str8('abc'), False)
-        self.assertEqual('abc' != str8('abc'), True)
+        self.assertEqual('abc' == str8(b'abc'), False)
+        self.assertEqual('abc' != str8(b'abc'), True)
 
     def test_comparison(self):
         # Comparisons:
diff --git a/Lib/test/test_unicodedata.py b/Lib/test/test_unicodedata.py
index 58fc73d..ff2dcf5 100644
--- a/Lib/test/test_unicodedata.py
+++ b/Lib/test/test_unicodedata.py
@@ -176,7 +176,7 @@
 
     def test_east_asian_width(self):
         eaw = self.db.east_asian_width
-        self.assertRaises(TypeError, eaw, str8('a'))
+        self.assertRaises(TypeError, eaw, str8(b'a'))
         self.assertRaises(TypeError, eaw, '')
         self.assertRaises(TypeError, eaw, 'ra')
         self.assertEqual(eaw('\x1e'), 'N')
diff --git a/Lib/test/testcodec.py b/Lib/test/testcodec.py
index e7f836b..0db18c1 100644
--- a/Lib/test/testcodec.py
+++ b/Lib/test/testcodec.py
@@ -36,7 +36,7 @@
 decoding_map = codecs.make_identity_dict(range(256))
 decoding_map.update({
         0x78: "abc", # 1-n decoding mapping
-        str8("abc"): 0x0078,# 1-n encoding mapping
+        str8(b"abc"): 0x0078,# 1-n encoding mapping
         0x01: None,   # decoding mapping to <undefined>
         0x79: "",    # decoding mapping to <remove character>
 })