diff --git a/RELEASE.md b/RELEASE.md
index 16dd3e0..2894487 100644
--- a/RELEASE.md
+++ b/RELEASE.md
@@ -1,5 +1,12 @@
 # modbus: Modbus Support - Release Notes
 
+## R3-4 (January XXX, 2024)
+- Added support for Modbus function 17, which is called Report Slave ID.
+  The Modbus specification says this is only supported for serial RTU and
+  serial ASCII communications.  It reports the Run Indicator Status byte,
+  and additional vendor defined data.
+  Thanks to Najm us Saqib from LBNL for this.
+
 ## R3-3 (December 7, 2023)
 - Moved the documentation from https://epics-modbus.readthedocs.io/en/latest/
   to Github pages, https://epics-modules.github.io/modbus.