diff --git a/linkcheck/url.py b/linkcheck/url.py
index 71433fbc..ac98e297 100644
--- a/linkcheck/url.py
+++ b/linkcheck/url.py
@@ -28,6 +28,7 @@ except ImportError:  # Python 2
     import urlparse
 
 import requests
+from builtins import str as str_text
 
 from . import log, LOG_CHECK
 
@@ -178,7 +179,7 @@ def idna_encode (host):
     to RFC 3490.
     @raise: UnicodeError if hostname is not properly IDN encoded.
     """
-    if host and isinstance(host, unicode):
+    if host and isinstance(host, str_text):
         try:
             host.encode('ascii')
             return host, False
@@ -258,7 +259,7 @@ def url_fix_wayback_query(path):
 
 def url_parse_query (query, encoding=None):
     """Parse and re-join the given CGI query."""
-    if isinstance(query, unicode):
+    if isinstance(query, str_text):
         if encoding is None:
             encoding = url_encoding
         query = query.encode(encoding, 'ignore')
@@ -301,7 +302,7 @@ def url_norm (url, encoding=None):
     @return: (normed url, idna flag)
     @rtype: tuple of length two
     """
-    if isinstance(url, unicode):
+    if isinstance(url, str_text):
         # try to decode the URL to ascii since urllib.unquote()
         # handles non-unicode strings differently
         try:
@@ -416,7 +417,7 @@ def url_quote (url):
 def url_quote_part (s, safechars='/', encoding=None):
     """Wrap urllib.quote() to support unicode strings. A unicode string
     is first converted to UTF-8. After that urllib.quote() is called."""
-    if isinstance(s, unicode):
+    if isinstance(s, str_text):
         if encoding is None:
             encoding = url_encoding
         s = s.encode(encoding, 'ignore')