--- a/src/net/timbusproject/context/converter/OWLExportCLI.java
+++ b/src/net/timbusproject/context/converter/OWLExportCLI.java
@@ -143,13 +143,19 @@
         String outputFilename = cmd.getOptionValue("output");
         String ontologyIRI = cmd.getOptionValue("iri");
 
+        File archiFile = new File(inputFilename);
+        File outputFile = new File(outputFilename);
+
+        if (ontologyIRI == null || ontologyIRI.trim().length() == 0) {
+            ontologyIRI = OWLExport.getDefaultIRI(outputFile);
+            System.out.println("Ontology IRI not specified, defaulting to " + ontologyIRI + ", computed from file " + outputFile.getName());
+        }
+
         // load model
-        File archiFile = new File(inputFilename);
         IArchimateModel model = loadModel(archiFile);
         System.out.println("Loaded model from " + archiFile.getAbsolutePath());
 
         // convert model
-        File outputFile = new File(outputFilename);
         OWLExport.exportToOwl(model, outputFile, ontologyIRI);
         System.out.println("Wrote converted file to " + outputFile.getAbsolutePath());