diff --git a/src/ontology/Makefile b/src/ontology/Makefile
index 06e8edf..f9610c4 100644
--- a/src/ontology/Makefile
+++ b/src/ontology/Makefile
@@ -404,6 +404,18 @@ $(ONT)-simple.owl: $(SRC) $(OTHER_SRC) $(SIMPLESEED) $(IMPORT_FILES)
 		$(ANNOTATE_ONTOLOGY_VERSION) \
 		--output $@.tmp.owl && mv $@.tmp.owl $@
 
+$(ONT)-base.obo: $(ONT)-base.owl
+	$(ROBOT) convert --input $< --check false -f obo -o $@.tmp.obo && grep -v ^owl-axioms $@.tmp.obo > $@ && rm $@.tmp.obo
+
+$(ONT)-simple.obo: $(ONT)-simple.owl
+	$(ROBOT) convert --input $< --check false -f obo -o $@.tmp.obo && grep -v ^owl-axioms $@.tmp.obo > $@ && rm $@.tmp.obo
+
+$(ONT)-full.obo: $(ONT)-full.owl
+	$(ROBOT) convert --input $< --check false -f obo -o $@.tmp.obo && grep -v ^owl-axioms $@.tmp.obo > $@ && rm $@.tmp.obo
+
+$(ONT)-non-classified.obo: $(ONT)-non-classified.owl
+	$(ROBOT) convert --input $< --check false -f obo -o $@.tmp.obo && grep -v ^owl-axioms $@.tmp.obo > $@ && rm $@.tmp.obo
+
 $(ONT).obo: $(ONT).owl
 	$(ROBOT) convert --input $< --check false -f obo -o $@.tmp.obo && grep -v ^owl-axioms $@.tmp.obo > $@ && rm $@.tmp.obo