diff --git a/semantica/triplet_store/blazegraph_store.py b/semantica/triplet_store/blazegraph_store.py
index 9a18faf3..4e139a57 100644
--- a/semantica/triplet_store/blazegraph_store.py
+++ b/semantica/triplet_store/blazegraph_store.py
@@ -395,7 +395,8 @@ class BlazegraphStore:
                 if " " in inner or ">" in inner:
                     raise ValueError(f"IRI contains invalid characters: {obj!r}")
                 return obj
-            return f"<{obj}>"
+            validated_obj = sparql_escaping.validate_uri(obj)
+            return f"<{validated_obj}>"
 
         escaped = self._escape_literal(obj)
         datatype = metadata.get("datatype") or metadata.get("literal_datatype")
diff --git a/semantica/triplet_store/rdf4j_store.py b/semantica/triplet_store/rdf4j_store.py
index cdf05061..594f6dd2 100644
--- a/semantica/triplet_store/rdf4j_store.py
+++ b/semantica/triplet_store/rdf4j_store.py
@@ -536,7 +536,8 @@ class RDF4JStore:
                 if " " in inner or ">" in inner:
                     raise ValueError(f"IRI contains invalid characters: {obj!r}")
                 return obj
-            return f"<{obj}>"
+            validated_obj = sparql_escaping.validate_uri(obj)
+            return f"<{validated_obj}>"
 
         escaped = sparql_escaping.escape_literal(obj)
         datatype = metadata.get("datatype") or metadata.get("literal_datatype")
diff --git a/tests/triplet_store/test_sparql_injection.py b/tests/triplet_store/test_sparql_injection.py
index 863efa85..d8bb0e48 100644
--- a/tests/triplet_store/test_sparql_injection.py
+++ b/tests/triplet_store/test_sparql_injection.py
@@ -17,7 +17,7 @@ before any query/update text is built.
 """
 
 import unittest
-from unittest.mock import MagicMock, patch
+from unittest.mock import patch
 
 from semantica.semantic_extract.triplet_extractor import Triplet
 from semantica.triplet_store.blazegraph_store import BlazegraphStore
@@ -84,7 +84,8 @@ class TestBlazegraphSparqlInjection(unittest.TestCase):
 
 
 class TestRDF4JSparqlInjection(unittest.TestCase):
-    def _make_store(self):
+    @patch.object(RDF4JStore, "_connect", autospec=True)
+    def _make_store(self, _mock_connect):
         return RDF4JStore(endpoint="http://localhost:9999/rdf4j", repository_id="mem")
 
     def test_triplets_to_ntriples_rejects_malicious_subject(self):