diff --git a/nh_eobs_api/controllers/route_api.py b/nh_eobs_api/controllers/route_api.py
index c9dfe4c3..2c85a599 100644
--- a/nh_eobs_api/controllers/route_api.py
+++ b/nh_eobs_api/controllers/route_api.py
@@ -403,6 +403,10 @@ def calculate_obs_score(self, *args, **kw):
                     'respiration_rate'
                 ]:
                     del data[key]
+
+        # iPad submits a key as an empty string which converter doesn't like
+        data = {k: v for k, v in data.items() if k}
+
         converted_data = converter(data, _logger.debug)
 
         score_dict = api_pool.get_activity_score(