diff --git a/internal-dev/obi-ext.owl b/internal-dev/obi-ext.owl
index 41c44466..32f03e5f 100644
--- a/internal-dev/obi-ext.owl
+++ b/internal-dev/obi-ext.owl
@@ -690,4 +690,14 @@
         </rdfs:subClassOf>
 </owl:Class>
 
+    <!-- http://purl.obolibrary.org/obo/OBI_0002167 -->
+
+    <owl:Class rdf:about="http://purl.obolibrary.org/obo/OBI_0002167">
+	<rdfs:subClassOf>
+            <owl:Restriction>
+                <owl:onProperty rdf:resource="http://www.bioassayontology.org/bao#BAO_0000208"/>
+                <owl:someValuesFrom rdf:resource="http://purl.obolibrary.org/obo/GO_0051641"/>
+            </owl:Restriction>
+        </rdfs:subClassOf>
+</owl:Class>
 </rdf:RDF>