diff --git a/geospaas_processing/converters/syntool/converter.py b/geospaas_processing/converters/syntool/converter.py
index 5f60cc73..deafc39a 100644
--- a/geospaas_processing/converters/syntool/converter.py
+++ b/geospaas_processing/converters/syntool/converter.py
@@ -220,7 +220,10 @@ def parse_converter_options(self, kwargs):
         """
         converter_options = self.converter_options.copy()
         converter_options_list = []
-        converter_options.update(kwargs.pop('converter_options', {}))
+        kwargs_converter_options = kwargs.pop('converter_options')
+        if not kwargs_converter_options:
+            kwargs_converter_options = {}
+        converter_options.update(kwargs_converter_options)
         if converter_options:
             converter_options_list.append('-opt')
             for key, value in converter_options.items():