diff --git a/owlapy/__init__.py b/owlapy/__init__.py
index 10939f0..8ce9b36 100644
--- a/owlapy/__init__.py
+++ b/owlapy/__init__.py
@@ -1 +1 @@
-__version__ = '0.1.2'
+__version__ = '0.1.3'
diff --git a/owlapy/owl2sparql/converter.py b/owlapy/owl2sparql/converter.py
index 9b6ef4c..3229fdf 100644
--- a/owlapy/owl2sparql/converter.py
+++ b/owlapy/owl2sparql/converter.py
@@ -631,9 +631,10 @@ def as_query(self,
 converter = Owl2SparqlConverter()
 
 
-def owl_expression_to_sparql(root_variable: str,
-                             ce: OWLClassExpression,
+def owl_expression_to_sparql(root_variable: str = "?x",
+                             ce: OWLClassExpression = None,
                              count: bool = False,
                              values: Optional[Iterable[OWLNamedIndividual]] = None,
-                             named_individuals: bool = False):
+                             named_individuals: bool = False)->str:
+    """Convert an OWL Class Expression (https://www.w3.org/TR/owl2-syntax/#Class_Expressions) into a SPARQL query"""
     return converter.as_query(root_variable, ce, count, values, named_individuals)
diff --git a/setup.py b/setup.py
index 5f50863..4c138d6 100644
--- a/setup.py
+++ b/setup.py
@@ -6,7 +6,7 @@
     name="owlapy",
     description="Owlapy is loosely based on owlapi - the java counterpart, "
                 "successfully representing the main owl objects in python.",
-    version="0.1.2",
+    version="0.1.3",
     packages=find_packages(),
     install_requires=[
         "pandas>=1.5.0",