diff --git a/src/datalad_cds/spec.py b/src/datalad_cds/spec.py
index ba67300..d3b87b0 100644
--- a/src/datalad_cds/spec.py
+++ b/src/datalad_cds/spec.py
@@ -42,7 +42,7 @@ def to_dict(self) -> Dict[str, Any]:
         }
 
     def to_json(self) -> str:
-        return json.dumps(self.to_dict(), separators=(",", ":"))
+        return json.dumps(self.to_dict(), separators=(",", ":"), sort_keys=True)
 
     def to_url(self) -> str:
         json_spec = self.to_json()