diff --git a/boltons/typeutils.py b/boltons/typeutils.py
index 462d408..6a70f22 100644
--- a/boltons/typeutils.py
+++ b/boltons/typeutils.py
@@ -53,8 +53,11 @@ def make_sentinel(name='_MISSING', var_name=None):
             def __reduce__(self):
                 return self.var_name
 
-        def __len__(self):
-            return 0
+        def __nonzero__(self):
+            return False
+
+        __bool__ = __nonzero__
+
     return Sentinel()
 
 
diff --git a/tests/test_typeutils.py b/tests/test_typeutils.py
new file mode 100644
index 0000000..80c6cc6
--- /dev/null
+++ b/tests/test_typeutils.py
@@ -0,0 +1,7 @@
+
+from boltons.typeutils import make_sentinel
+
+
+def test_sentinel_falsiness():
+    not_set = make_sentinel('not_set')
+    assert not not_set