diff --git a/lib/core/settings.py b/lib/core/settings.py
index efd1ff6fd..bb771fa38 100644
--- a/lib/core/settings.py
+++ b/lib/core/settings.py
@@ -20,7 +20,7 @@ from thirdparty import six
 from thirdparty.six import unichr as _unichr
 
 # sqlmap version (<major>.<minor>.<month>.<monthly commit>)
-VERSION = "1.7.2.15"
+VERSION = "1.7.2.16"
 TYPE = "dev" if VERSION.count('.') > 2 and VERSION.split('.')[-1] != '0' else "stable"
 TYPE_COLORS = {"dev": 33, "stable": 90, "pip": 34}
 VERSION_STRING = "sqlmap/%s#%s" % ('.'.join(VERSION.split('.')[:-1]) if VERSION.count('.') > 2 and VERSION.split('.')[-1] == '0' else VERSION, TYPE)
diff --git a/lib/techniques/blind/inference.py b/lib/techniques/blind/inference.py
index d7353da7e..52bea1163 100644
--- a/lib/techniques/blind/inference.py
+++ b/lib/techniques/blind/inference.py
@@ -26,6 +26,7 @@ from lib.core.common import goGoodSamaritan
 from lib.core.common import hashDBRetrieve
 from lib.core.common import hashDBWrite
 from lib.core.common import incrementCounter
+from lib.core.common import isDigit
 from lib.core.common import isListLike
 from lib.core.common import safeStringFormat
 from lib.core.common import singleTimeWarnMessage
@@ -61,6 +62,7 @@ from lib.request.connect import Connect as Request
 from lib.utils.progress import ProgressBar
 from lib.utils.safe2bin import safecharencode
 from lib.utils.xrange import xrange
+from thirdparty import six
 
 def bisection(payload, expression, length=None, charsetType=None, firstChar=None, lastChar=None, dump=False):
     """
@@ -163,7 +165,7 @@ def bisection(payload, expression, length=None, charsetType=None, firstChar=None
         else:
             expressionUnescaped = unescaper.escape(expression)
 
-        if hasattr(length, "isdigit") and length.isdigit() or isinstance(length, int):
+        if isinstance(length, six.string_types) and isDigit(length) or isinstance(length, int):
             length = int(length)
         else:
             length = None