diff --git a/docs/release-notes/2411.rst b/docs/release-notes/2411.rst
new file mode 100644
index 00000000..1de94d0a
--- /dev/null
+++ b/docs/release-notes/2411.rst
@@ -0,0 +1,15 @@
+24.11 Release notes
+===================
+
+.. role:: nix(code)
+   :language: nix
+
+Breaking changes
+----------------
+
+- the :ref:`pkg-support.modbus` support module was upgraded from 3-2 to 3-4,
+  which changed the name of the ``modbus.dbd`` file.
+  This file wasn't meant to be used,
+  but if you used it by mistake,
+  make sure to include ``modbusSupport.dbd``,
+  and ``drvAsynIPPort.dbd`` or ``drvAsynSerialPort.dbd`` instead.
diff --git a/pkgs/epnix/support/modbus/default.nix b/pkgs/epnix/support/modbus/default.nix
index 1eb6200e..58854a04 100644
--- a/pkgs/epnix/support/modbus/default.nix
+++ b/pkgs/epnix/support/modbus/default.nix
@@ -7,14 +7,14 @@
 }:
 mkEpicsPackage rec {
   pname = "modbus";
-  version = "3-2";
+  version = "3-4";
   varname = "MODBUS";
 
   src = fetchFromGitHub {
     owner = "epics-modules";
     repo = pname;
-    rev = "R3-2";
-    hash = "sha256-k8MSgNxib4JT0JTbs0BOm75HIVvxHuVPPlo7VcMCnzg=";
+    rev = "R${version}";
+    hash = "sha256-0v6eLWdjgYKbFOHWaW1NSfN/gG5XHVRD9jan55dXWW0=";
   };
 
   propagatedBuildInputs = with epnix.support; [asyn];