diff --git a/src/simapy/sima_writer.py b/src/simapy/sima_writer.py
index 577da2b8..b1d77266 100644
--- a/src/simapy/sima_writer.py
+++ b/src/simapy/sima_writer.py
@@ -15,12 +15,12 @@
 class SIMAWriter():
     """ Export entites as SIMA objects"""
 
-    def write(self, models: Sequence[MOAO], filename: str, indent=0):
+    def write(self, models: Sequence[MOAO] | MOAO, filename: str, indent=0):
         """Write SIMA models to file"""
         content = self.__to_model_content(models)
         DMTWriter().write(content, filename, indent=indent)
 
-    def __to_model_content(self, models: Sequence[Entity]) -> ModelContent:
+    def __to_model_content(self, models: Sequence[Entity] | Entity) -> ModelContent:
         content = ModelContent()
         header = Header()
 
@@ -28,7 +28,10 @@ def __to_model_content(self, models: Sequence[Entity]) -> ModelContent:
             header.packages.append(PackageInfo(name=name,version=version))
 
         content.header = header
-        content.contents.extend(models)
+        if isinstance(models, Entity):
+            content.contents.append(models)
+        else:
+            content.contents.extend(models)
         return content
 
     def to_dict(self, models: Sequence[MOAO]) -> Dict: