diff --git a/python/src/model.rs b/python/src/model.rs
index 8fbeecbe..f92b862d 100644
--- a/python/src/model.rs
+++ b/python/src/model.rs
@@ -20,7 +20,7 @@ use std::vec::IntoIter;
 ///
 /// >>> str(NamedNode('http://example.com'))
 /// '<http://example.com>'
-#[pyclass(name = "NamedNode", module = "pyoxigraph")]
+#[pyclass(frozen, name = "NamedNode", module = "pyoxigraph")]
 #[pyo3(text_signature = "(value)")]
 #[derive(Eq, PartialEq, Ord, PartialOrd, Debug, Clone, Hash)]
 pub struct PyNamedNode {
@@ -144,7 +144,7 @@ impl PyNamedNode {
 ///
 /// >>> str(BlankNode('ex'))
 /// '_:ex'
-#[pyclass(name = "BlankNode", module = "pyoxigraph")]
+#[pyclass(frozen, name = "BlankNode", module = "pyoxigraph")]
 #[pyo3(text_signature = "(value = None)")]
 #[derive(Eq, PartialEq, Debug, Clone, Hash)]
 pub struct PyBlankNode {
@@ -280,7 +280,7 @@ impl PyBlankNode {
 /// '"example"@en'
 /// >>> str(Literal('11', datatype=NamedNode('http://www.w3.org/2001/XMLSchema#integer')))
 /// '"11"^^<http://www.w3.org/2001/XMLSchema#integer>'
-#[pyclass(name = "Literal", module = "pyoxigraph")]
+#[pyclass(frozen, name = "Literal", module = "pyoxigraph")]
 #[pyo3(text_signature = "(value, *, datatype = None, language = None)")]
 #[derive(Eq, PartialEq, Debug, Clone, Hash)]
 pub struct PyLiteral {
@@ -427,7 +427,7 @@ impl PyLiteral {
 }
 
 /// The RDF `default graph name <https://www.w3.org/TR/rdf11-concepts/#dfn-default-graph>`_.
-#[pyclass(name = "DefaultGraph", module = "pyoxigraph")]
+#[pyclass(frozen, name = "DefaultGraph", module = "pyoxigraph")]
 #[pyo3(text_signature = "()")]
 #[derive(Eq, PartialEq, Debug, Clone, Copy, Hash)]
 pub struct PyDefaultGraph {}
@@ -625,7 +625,7 @@ impl IntoPy<PyObject> for PyTerm {
 /// A triple could also be easily destructed into its components:
 ///
 /// >>> (s, p, o) = Triple(NamedNode('http://example.com'), NamedNode('http://example.com/p'), Literal('1'))
-#[pyclass(name = "Triple", module = "pyoxigraph")]
+#[pyclass(frozen, name = "Triple", module = "pyoxigraph")]
 #[derive(Eq, PartialEq, Debug, Clone, Hash)]
 #[pyo3(text_signature = "(subject, predicate, object)")]
 pub struct PyTriple {
@@ -824,7 +824,7 @@ impl IntoPy<PyObject> for PyGraphName {
 /// A quad could also be easily destructed into its components:
 ///
 /// >>> (s, p, o, g) = Quad(NamedNode('http://example.com'), NamedNode('http://example.com/p'), Literal('1'), NamedNode('http://example.com/g'))
-#[pyclass(name = "Quad", module = "pyoxigraph")]
+#[pyclass(frozen, name = "Quad", module = "pyoxigraph")]
 #[pyo3(text_signature = "(subject, predicate, object, graph_name = None)")]
 #[derive(Eq, PartialEq, Debug, Clone, Hash)]
 pub struct PyQuad {
@@ -1012,7 +1012,7 @@ impl PyQuad {
 ///
 /// >>> str(Variable('foo'))
 /// '?foo'
-#[pyclass(name = "Variable", module = "pyoxigraph")]
+#[pyclass(frozen, name = "Variable", module = "pyoxigraph")]
 #[pyo3(text_signature = "(value)")]
 #[derive(Eq, PartialEq, Debug, Clone, Hash)]
 pub struct PyVariable {
diff --git a/python/src/sparql.rs b/python/src/sparql.rs
index 1cd0e1b2..01298fa6 100644
--- a/python/src/sparql.rs
+++ b/python/src/sparql.rs
@@ -88,7 +88,7 @@ pub fn query_results_to_python(py: Python<'_>, results: QueryResults) -> PyObjec
 /// >>> s, p, o = solution
 /// >>> s
 /// <NamedNode value=http://example.com>
-#[pyclass(unsendable, name = "QuerySolution", module = "pyoxigraph")]
+#[pyclass(frozen, unsendable, name = "QuerySolution", module = "pyoxigraph")]
 pub struct PyQuerySolution {
     inner: QuerySolution,
 }