diff --git a/pyiron_ontology/parser.py b/pyiron_ontology/parser.py
index ee6afbd..564aace 100644
--- a/pyiron_ontology/parser.py
+++ b/pyiron_ontology/parser.py
@@ -52,8 +52,10 @@ def get_triples(data, EX):
             full_key = data["label"] + f".{io_}." + key
             label = EX[full_key]
             graph.add((label, RDFS.label, Literal(full_key)))
-            graph.add((label, RDF.type, d["uri"]))
-            graph.add((label, RDF.value, Literal(d["value"])))
+            if d["uri"]:
+                graph.add((label, RDF.type, d["uri"]))
+            if d["value"]:
+                graph.add((label, RDF.value, Literal(d["value"])))
             graph.add((label, EX[io_[:-1] + "Of"], EX[data["label"]]))
             if d["units"] is not None:
                 graph.add((label, EX.hasUnits, EX[d["units"]]))
diff --git a/tests/unit/test_parser.py b/tests/unit/test_parser.py
index 393458b..8f35b2f 100644
--- a/tests/unit/test_parser.py
+++ b/tests/unit/test_parser.py
@@ -1,7 +1,8 @@
 import unittest
-from pyiron_ontology.parser import get_inputs_and_outputs
+from pyiron_ontology.parser import get_inputs_and_outputs, get_triples
 from pyiron_workflow import Workflow
 from semantikon.typing import u
+from rdflib import Namespace
 
 
 @Workflow.wrap.as_function_node("speed")
@@ -19,6 +20,15 @@ def test_parser(self):
         for label in ["inputs", "outputs", "function", "label"]:
             self.assertIn(label, output_dict)
 
+    def test_triples(self):
+        EX = Namespace("http://example.org/")
+        speed = calculate_speed()
+        data = get_inputs_and_outputs(speed)
+        graph = get_triples(data, EX)
+        self.assertGreater(
+            len(list(graph.triples((None, EX.hasUnits, EX["meter/second"])))), 0
+        )
+
 
 if __name__ == "__main__":
     unittest.main()