diff --git a/api_deploy/schema.py b/api_deploy/schema.py
index 1f73623..c54830b 100644
--- a/api_deploy/schema.py
+++ b/api_deploy/schema.py
@@ -1,12 +1,35 @@
 from typing import Dict
-import yaml
+import io
+import ruyaml
 
-yaml.Dumper.ignore_aliases = lambda *args: True
+_yaml = ruyaml.YAML(typ='safe')
+# avoid YAML aliases/anchors in output
+_yaml.representer.ignore_aliases = lambda *args: True
+
+
+def _dump_to_string(data, sort_keys=False):
+    # Optional key sorting to mimic previous behavior when requested
+    def _sort(obj):
+        if isinstance(obj, dict):
+            # sort by key, recursively
+            return {k: _sort(obj[k]) for k in sorted(obj.keys())}
+        if isinstance(obj, list):
+            return [
+                _sort(i) for i in obj
+            ]
+        return obj
+
+    if sort_keys:
+        data = _sort(data)
+    stream = io.StringIO()
+    _yaml.dump(data, stream)
+    return stream.getvalue()
 
 
 class YamlDict(Dict):
     def __init__(self, schema) -> None:
-        content = yaml.load(schema, yaml.Loader) or {}
+        # ruyaml.YAML.load accepts str, bytes, and file-like objects
+        content = _yaml.load(schema) or {}
         super().__init__(content)
 
     @classmethod
@@ -19,7 +42,7 @@ def to_file(self, file_path):
             target.write(self.dump())
 
     def dump(self, sort_keys=False):
-        return yaml.dump(self, sort_keys=sort_keys)
+        return _dump_to_string(self, sort_keys=sort_keys)
 
 
 class Schema(YamlDict):
@@ -34,4 +57,4 @@ def dump(self, sort_keys=False):
             'x-amazon-apigateway-request-validators': self.get('x-amazon-apigateway-request-validators', {}),
             'x-amazon-apigateway-minimum-compression-size': 0                                   ,
         }
-        return yaml.dump(data, sort_keys=sort_keys)
+        return _dump_to_string(data, sort_keys=sort_keys)
diff --git a/setup.py b/setup.py
index bfd3c25..ead308a 100644
--- a/setup.py
+++ b/setup.py
@@ -15,7 +15,7 @@ def readme():
     'click>=8.1.3, <9',
     'mergedeep>=1.3.4',
     'boto3>=1.26.118',
-    'PyYAML>=6.0',
+    'ruyaml==0.91',
     'requests>=2.31.0',
     'Jinja2==3.1.2',
     'urllib3<2',
diff --git a/tests/openapi/complex_source.yml b/tests/openapi/complex_source.yml
index e8edff7..6eb831d 100644
--- a/tests/openapi/complex_source.yml
+++ b/tests/openapi/complex_source.yml
@@ -403,6 +403,13 @@ components:
           enum:
             - draft
             - submitted
+        offerCode:
+          type: string
+          readOnly: true
+          enum:
+            - "0116"
+            - "0118"
+            - "0119"
         stateTransitions:
           $ref: "#/components/schemas/StateTransitionList"
         _meta:
diff --git a/tests/openapi/complex_target.yml b/tests/openapi/complex_target.yml
index 439c1f5..d70e421 100644
--- a/tests/openapi/complex_target.yml
+++ b/tests/openapi/complex_target.yml
@@ -1252,6 +1252,7 @@ components:
                 - attachments
                 - comment
                 - state
+                - offerCode
                 - stateTransitions
                 - _meta
                 - _links
@@ -1307,6 +1308,13 @@ components:
                     enum:
                     - draft
                     - submitted
+                  offerCode:
+                    type: string
+                    readOnly: true
+                    enum:
+                      - "0116"
+                      - "0118"
+                      - "0119"
                   stateTransitions:
                     type: array
                     readOnly: true
@@ -1704,6 +1712,7 @@ components:
       - attachments
       - comment
       - state
+      - offerCode
       - stateTransitions
       - _meta
       - _links
@@ -1759,6 +1768,13 @@ components:
           enum:
           - draft
           - submitted
+        offerCode:
+          type: string
+          readOnly: true
+          enum:
+            - "0116"
+            - "0118"
+            - "0119"
         stateTransitions:
           type: array
           readOnly: true