update docs to fix #1481
diff --git a/docs/development/c-bindings.rst b/docs/development/c-bindings.rst
index 5696337..10d5fc1 100644
--- a/docs/development/c-bindings.rst
+++ b/docs/development/c-bindings.rst
@@ -7,6 +7,10 @@
Bindings live in :py:mod:`cryptography.hazmat.bindings`.
+When modifying the bindings you will need to recompile the C extensions to
+test the changes. This can be accomplished with ``pip install -e .`` in the
+project root. If you do not do this a ``RuntimeError`` will be raised.
+
Style guide
-----------