diff --git a/CHANGELOG.md b/CHANGELOG.md
index 00b1f0f..413de8e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,9 @@
 # Changelog
 
 This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+## [3.18.4] - 2025-03-16
+  - Add unratified Svrsw60t59b extension
+
 ## [3.18.3] - 2024-05-28
   - exclude Svnapot from march generation. fixes #178.
   - log raw error messages from ruamel while loading yamls. fixes #179.
diff --git a/riscv_config/__init__.py b/riscv_config/__init__.py
index 3821f42..94e44d8 100644
--- a/riscv_config/__init__.py
+++ b/riscv_config/__init__.py
@@ -1,4 +1,4 @@
 from pkgutil import extend_path
 __path__ = extend_path(__path__, __name__)
-__version__ = '3.18.3'
+__version__ = '3.18.4'
 
diff --git a/riscv_config/constants.py b/riscv_config/constants.py
index 2913757..b39de1e 100644
--- a/riscv_config/constants.py
+++ b/riscv_config/constants.py
@@ -33,7 +33,7 @@
         "Zpn", "Zpsf"
 ] + Zve_extensions + Zvl_extensions
 
-S_extensions = ['Smrnmi','Smdbltrp', 'Ssdbltrp', 'Svnapot','Svadu', 'Sddbltrp', 'Sdext']
+S_extensions = ['Smrnmi','Smdbltrp', 'Ssdbltrp', 'Svnapot','Svadu', 'Sddbltrp', 'Sdext', 'Svrsw60t59b']
 
 sub_extensions = Z_extensions + S_extensions
 
diff --git a/setup.cfg b/setup.cfg
index c6427e0..e139e47 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -1,5 +1,5 @@
 [bumpversion]
-current_version = 3.18.3
+current_version = 3.18.4
 commit = True
 tag = True