diff --git a/netlib/strutils.py b/netlib/strutils.py
index a51df8868..32e779271 100644
--- a/netlib/strutils.py
+++ b/netlib/strutils.py
@@ -57,8 +57,8 @@ def escape_control_characters(text, keep_spacing=True):
     Args:
         keep_spacing: If True, tabs and newlines will not be replaced.
     """
-    # type: (six.text_type) -> six.text_type
-    if not isinstance(text, six.text_type):
+    # type: (six.string_types) -> six.text_type
+    if not isinstance(text, six.string_types):
         raise ValueError("text type must be unicode but is {}".format(type(text).__name__))
 
     trans = _control_char_trans_newline if keep_spacing else _control_char_trans
diff --git a/test/netlib/test_strutils.py b/test/netlib/test_strutils.py
index 68bfdb942..7c3eacc69 100644
--- a/test/netlib/test_strutils.py
+++ b/test/netlib/test_strutils.py
@@ -38,8 +38,9 @@ def test_escape_control_characters():
         u'=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~.'
     )
 
-    with tutils.raises(ValueError):
-        strutils.escape_control_characters(b"foo")
+    if not six.PY2:
+        with tutils.raises(ValueError):
+            strutils.escape_control_characters(b"foo")
 
 
 def test_bytes_to_escaped_str():