diff --git a/cloudinary/auth_token.py b/cloudinary/auth_token.py
index 8ddeacd..417c990 100644
--- a/cloudinary/auth_token.py
+++ b/cloudinary/auth_token.py
@@ -12,6 +12,9 @@
 
 def generate(url=None, acl=None, start_time=None, duration=None,
              expiration=None, ip=None, key=None, token_name=AUTH_TOKEN_NAME, **_):
+    start_time = _ensure_int(start_time)
+    duration = _ensure_int(duration)
+    expiration = _ensure_int(expiration)
 
     if expiration is None:
         if duration is not None:
@@ -52,3 +55,22 @@ def _escape_to_lower(url):
     escaped_url = smart_escape(url, unsafe=AUTH_TOKEN_UNSAFE_RE)
     escaped_url = re.sub(r"%[0-9A-F]{2}", lambda x: x.group(0).lower(), escaped_url)
     return escaped_url
+
+def _ensure_int(value):
+    """
+    Ensures the input value is an integer.
+    Attempts to cast it to an integer if it is not already.
+
+    :param value: The value to ensure as an integer.
+    :type value: Any
+    :return: The integer value.
+    :rtype: int
+    :raises ValueError: If the value cannot be converted to an integer.
+    """
+    if isinstance(value, int) or not value:
+        return value
+
+    try:
+        return int(value)
+    except (ValueError, TypeError):
+        raise ValueError("Value '" + value + "' must be an integer.")
diff --git a/test/test_auth_token.py b/test/test_auth_token.py
index 9160731..349365f 100644
--- a/test/test_auth_token.py
+++ b/test/test_auth_token.py
@@ -11,9 +11,11 @@
 class AuthTokenTest(unittest.TestCase):
     def setUp(self):
         self.url_backup = os.environ.get("CLOUDINARY_URL")
-        os.environ["CLOUDINARY_URL"] = "cloudinary://a:b@test123"
+        os.environ["CLOUDINARY_URL"] = ("cloudinary://a:b@test123?"
+                                        "auth_token[duration]=300"
+                                        "&auth_token[start_time]=11111111"
+                                        "&auth_token[key]=" + KEY)
         cloudinary.reset_config()
-        cloudinary.config(auth_token={"key": KEY, "duration": 300, "start_time": 11111111})
 
     def tearDown(self):
         with ignore_exception():
@@ -93,6 +95,16 @@ def test_generate_token_string(self):
             "8e39600cc18cec339b21fe2b05fcb64b98de373355f8ce732c35710d8b10259f"
         )
 
+    def test_generate_token_string_from_string_values(self):
+        user = "foobar"
+        token_options = {"key": KEY, "duration": "300", "acl": "/*/t_%s" % user, "start_time": "222222222"}
+        cookie_token = cloudinary.utils.generate_auth_token(**token_options)
+        self.assertEqual(
+            cookie_token,
+            "__cld_token__=st=222222222~exp=222222522~acl=%2f*%2ft_foobar~hmac="
+            "8e39600cc18cec339b21fe2b05fcb64b98de373355f8ce732c35710d8b10259f"
+        )
+
     def test_should_ignore_url_if_acl_is_provided(self):
         token_options = {"key": KEY, "duration": 300, "acl": '/image/*', "start_time": 222222222}
         acl_token = cloudinary.utils.generate_auth_token(**token_options)