diff --git a/ldap3/utils/port_validators.py b/ldap3/utils/port_validators.py
index c46b752c..91a434be 100644
--- a/ldap3/utils/port_validators.py
+++ b/ldap3/utils/port_validators.py
@@ -4,7 +4,7 @@
 def check_port(port):
     """ Check if a port is valid. Return an error message indicating what is invalid if something isn't valid. """
     if isinstance(port, int):
-        if port not in range(0, 65535):
+        if port not in range(0, 65536):
             return 'Source port must in range from 0 to 65535'
     else:
         return 'Source port must be an integer'
@@ -20,7 +20,7 @@ def check_port_and_port_list(port, port_list):
         return 'Cannot specify both a source port and a source port list'
     elif port is not None:
         if isinstance(port, int):
-            if port not in range(0, 65535):
+            if port not in range(0, 65536):
                 return 'Source port must in range from 0 to 65535'
         else:
             return 'Source port must be an integer'
diff --git a/test/testValidators.py b/test/testValidators.py
index 1f8dccc2..8e6d5370 100644
--- a/test/testValidators.py
+++ b/test/testValidators.py
@@ -3,6 +3,8 @@
 
 from ldap3.protocol.formatters.validators import validate_integer, validate_boolean, validate_bytes, validate_generic_single_value, validate_time, validate_zero_and_minus_one_and_positive_int
 from ldap3.core.timezone import OffsetTzInfo
+from ldap3.utils.port_validators import check_port, check_port_and_port_list
+
 
 class Test(unittest.TestCase):
     def test_int_validator_valid_number(self):
@@ -202,3 +204,17 @@ def test_validate_minus_one_zero_greater_than_zero(self):
         self.assertTrue(validated)
         validated = validate_zero_and_minus_one_and_positive_int('-2')
         self.assertFalse(validated)
+
+    def test_check_port(self):
+        assert check_port("0") == 'Source port must be an integer'
+        assert check_port(0) is None
+        assert check_port(65535) is None
+        assert check_port(-1) == 'Source port must in range from 0 to 65535'
+        assert check_port(65536) == 'Source port must in range from 0 to 65535'
+
+    def test_check_port_and_port_list(self):
+        assert check_port_and_port_list("0", None) == 'Source port must be an integer'
+        assert check_port_and_port_list(0, None) is None
+        assert check_port_and_port_list(65535, None) is None
+        assert check_port_and_port_list(-1, None) == 'Source port must in range from 0 to 65535'
+        assert check_port_and_port_list(65536, None) == 'Source port must in range from 0 to 65535'