diff --git a/documentation/RELEASE_NOTES.md b/documentation/RELEASE_NOTES.md
index 948a17c21..363105e87 100644
--- a/documentation/RELEASE_NOTES.md
+++ b/documentation/RELEASE_NOTES.md
@@ -6,6 +6,14 @@ This version of EPICS Base has not been released yet.
 
 <!-- Insert new items immediately below here ... -->
 
+### Fix timers on MS Windows for non-EPICS threads
+
+The waitable timer changes in 3.15.9 broke calls to `epicsThreadSleep()` and
+similar routines that used timers (including `ca_pend_event()`) when made from
+threads that were not started using the epicsThread APIs.
+[This problem](https://github.com/epics-base/epics-base/pull/200)
+[has now been fixed](https://github.com/epics-base/epics-base/pull/201).
+
 ## Changes made between 3.15.8 and 3.15.9
 
 ### Use waitable timers on Microsoft Windows