diff --git a/doc/bitbake-user-manual/bitbake-user-manual-metadata.rst b/doc/bitbake-user-manual/bitbake-user-manual-metadata.rst
index 621aab253..eef1f9624 100644
--- a/doc/bitbake-user-manual/bitbake-user-manual-metadata.rst
+++ b/doc/bitbake-user-manual/bitbake-user-manual-metadata.rst
@@ -2264,6 +2264,14 @@ The specified <namespace> is imported automatically, and if the imported
 module specifies an attribute named ``BBIMPORTS``, that list of
 sub-modules is iterated and imported too.
 
+Additionally, Bitbake will detect usage of functions from such a
+library and include them in task hashes, so changes in those functions
+trigger task rebuilds.  Note that only functions inside modules
+declared using ``BBIMPORTS`` benefit from this dependency tracking,
+any name defined directly in the specified namespace (e.g. in
+`<namespace>/__init__.py`, or in a library hat would be defined as
+`<namespace>.py`) would *not* benefit from this tracking.
+
 Testing and Debugging BitBake Python code
 -----------------------------------------