diff --git a/docs/hazmat/primitives/interfaces.rst b/docs/hazmat/primitives/interfaces.rst
index 11cff51..e798c0e 100644
--- a/docs/hazmat/primitives/interfaces.rst
+++ b/docs/hazmat/primitives/interfaces.rst
@@ -56,6 +56,18 @@
         The name may be used by a backend to influence the operation of a
         cipher in conjunction with the algorithm's name.
 
+    .. method:: validate_for_algorithm(algorithm)
+
+        :param CipherAlgorithm algorithm:
+
+        Checks that the combination of this mode with the provided algorithm
+        meets any necessary invariants. This should raise an exception if they
+        are not met.
+
+        For example, the :class:`~cryptography.hazmat.primitives.modes.CBC`
+        mode uses this method to check that the provided initialization
+        vector's length matches the block size of the algorithm.
+
 
 .. class:: ModeWithInitializationVector