diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 4fb2509..8db17dc 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -1,6 +1,12 @@
 Changelog
 =========
 
+1.6.6 (2023-10-30)
+------------------
+
+ - (Fixed) Backward incompatible change in ``ruamel.yaml``.
+
+
 1.6.5 (2023-05-08)
 ------------------
 
diff --git a/setup.py b/setup.py
index f8951de..f48ffa7 100644
--- a/setup.py
+++ b/setup.py
@@ -46,9 +46,9 @@
     keywords='statechart state machine interpreter model uml scxml harel',
 
     packages=find_packages(exclude=['docs', 'tests']),
-    python_requires='>=3.5',
+    python_requires='>=3.7',
     install_requires=[
-        'ruamel.yaml>=0.12.10',
+        'ruamel.yaml>=0.18.2',
         'schema>=0.5.0',
         'behave>=1.2.6',
     ],