diff --git a/Objects/stringlib/formatter.h b/Objects/stringlib/formatter.h
index 22dd292..05ccfea 100644
--- a/Objects/stringlib/formatter.h
+++ b/Objects/stringlib/formatter.h
@@ -778,7 +778,7 @@
     /* This is to allow things like u''.format('') */
     if (!PyArg_ParseTuple(args, "O:__format__", &format_spec))
         goto done;
-    if (!(PyString_Check(format_spec) || PyUnicode_Check(format_spec))) {
+    if (!(PyBytes_Check(format_spec) || PyUnicode_Check(format_spec))) {
         PyErr_Format(PyExc_TypeError, "__format__ arg must be str "
 		     "or unicode, not %s", Py_TYPE(format_spec)->tp_name);
 	goto done;
diff --git a/Objects/stringlib/string_format.h b/Objects/stringlib/string_format.h
index be8e8080..2e9c7ef 100644
--- a/Objects/stringlib/string_format.h
+++ b/Objects/stringlib/string_format.h
@@ -496,7 +496,7 @@
 #if PY_VERSION_HEX >= 0x03000000
     assert(PyUnicode_Check(result));
 #else
-    assert(PyString_Check(result) || PyUnicode_Check(result));
+    assert(PyBytes_Check(result) || PyUnicode_Check(result));
 
     /* Convert result to our type.  We could be str, and result could
        be unicode */
diff --git a/Objects/stringlib/stringdefs.h b/Objects/stringlib/stringdefs.h
index daaa2e2..bdc3a29 100644
--- a/Objects/stringlib/stringdefs.h
+++ b/Objects/stringlib/stringdefs.h
@@ -6,7 +6,7 @@
    compiled as unicode. */
 #define STRINGLIB_IS_UNICODE     0
 
-#define STRINGLIB_OBJECT         PyStringObject
+#define STRINGLIB_OBJECT         PyBytesObject
 #define STRINGLIB_CHAR           char
 #define STRINGLIB_TYPE_NAME      "string"
 #define STRINGLIB_PARSE_CODE     "S"
@@ -16,13 +16,13 @@
 #define STRINGLIB_TOUPPER        toupper
 #define STRINGLIB_TOLOWER        tolower
 #define STRINGLIB_FILL           memset
-#define STRINGLIB_STR            PyString_AS_STRING
-#define STRINGLIB_LEN            PyString_GET_SIZE
-#define STRINGLIB_NEW            PyString_FromStringAndSize
-#define STRINGLIB_RESIZE         _PyString_Resize
-#define STRINGLIB_CHECK          PyString_Check
+#define STRINGLIB_STR            PyBytes_AS_STRING
+#define STRINGLIB_LEN            PyBytes_GET_SIZE
+#define STRINGLIB_NEW            PyBytes_FromStringAndSize
+#define STRINGLIB_RESIZE         _PyBytes_Resize
+#define STRINGLIB_CHECK          PyBytes_Check
 #define STRINGLIB_CMP            memcmp
 #define STRINGLIB_TOSTR          PyObject_Str
-#define STRINGLIB_GROUPING       _PyString_InsertThousandsGrouping
+#define STRINGLIB_GROUPING       _PyBytes_InsertThousandsGrouping
 
 #endif /* !STRINGLIB_STRINGDEFS_H */