diff --git a/slugify/slugify.py b/slugify/slugify.py
index f4e5faf..abfc099 100644
--- a/slugify/slugify.py
+++ b/slugify/slugify.py
@@ -183,6 +183,15 @@ def slugify(
     """
     if algorithm not in ('legacy', 'modern'):
         raise ValueError("algorithm must be 'legacy' or 'modern'")
+    # bool is an int subclass: max_length=True previously truncated to 1 char.
+    if isinstance(max_length, bool) or not isinstance(max_length, int):
+        raise TypeError(
+            f"max_length must be an int, not {type(max_length).__name__}"
+        )
+    if not isinstance(separator, str):
+        raise TypeError(
+            f"separator must be str, not {type(separator).__name__}"
+        )
     if not isinstance(text, str):
         if not isinstance(text, (bytes, bytearray)):
             raise TypeError(f'text must be str, bytes or bytearray, not {type(text).__name__}')
diff --git a/test.py b/test.py
index fcec4b6..32aa0ab 100644
--- a/test.py
+++ b/test.py
@@ -241,6 +241,16 @@ def test_pre_translation(self):
         self.assertEqual(PRE_TRANSLATIONS, [('Ю', 'U'), ('Щ', 'Sch'), ('У', 'Y'), ('Х', 'H'), ('Я', 'Ya'), ('Ё', 'E'), ('ё', 'e'), ('я', 'ya'), ('х', 'h'), ('у', 'y'), ('щ', 'sch'), ('ю', 'u'), ('Ü', 'Ue'), ('Ö', 'Oe'), ('Ä', 'Ae'), ('ä', 'ae'), ('ö', 'oe'), ('ü', 'ue'), ('Ϋ́', 'Y'), ('Ϋ', 'Y'), ('Ύ', 'Y'), ('Υ', 'Y'), ('Χ', 'Ch'), ('χ', 'ch'), ('Ξ', 'X'), ('ϒ', 'Y'), ('υ', 'y'), ('ύ', 'y'), ('ϋ', 'y'), ('ΰ', 'y')])
 
 
+
+    def test_max_length_rejects_bool(self):
+        with self.assertRaises(TypeError):
+            slugify("Hello World", max_length=True)
+        with self.assertRaises(TypeError):
+            slugify("Hello World", max_length=1.5)
+        with self.assertRaises(TypeError):
+            slugify("Hello", separator=None)
+        self.assertEqual(slugify("Hello World", max_length=5), "hello")
+
 class TestSlugifyUnicode(unittest.TestCase):
     def test_extraneous_seperators(self):