diff --git a/docs/api/srfi/18.md b/docs/api/srfi/18.md
index 28bda540..7d81b319 100644
--- a/docs/api/srfi/18.md
+++ b/docs/api/srfi/18.md
@@ -4,6 +4,12 @@ The `(srfi 18)` library provides multithreading support.
 
 See the [Multithreading support SRFI documentation](http://srfi.schemers.org/srfi-18/srfi-18.html) for more information.
 
+## Limitations
+
+Currently, ``thread-join!`` is not provided. While this is not an essential
+primitive and can be worked around, code that relies on ``thread-join!`` being
+present in this implementation will fail to compile.
+
 - [`thread?`](#thread)
 - [`make-thread`](#make-thread)
 - [`thread-name`](#thread-name)