diff --git a/weave/trace_server/objects_query_builder.py b/weave/trace_server/objects_query_builder.py
index 953141c9c30..df6ed522cc7 100644
--- a/weave/trace_server/objects_query_builder.py
+++ b/weave/trace_server/objects_query_builder.py
@@ -176,11 +176,10 @@ def add_is_op_condition(self, is_op: bool) -> None:
             self._conditions.append("is_op = 0")
 
     def add_base_object_classes_condition(self, base_object_classes: list[str]) -> None:
-        param_key = "base_object_classes"
         self._conditions.append(
-            f"base_object_classes IN {{{param_key}: Array(String)}}"
+            "base_object_class IN {base_object_classes: Array(String)}"
         )
-        self.parameters.update({param_key: base_object_classes})
+        self.parameters.update({"base_object_classes": base_object_classes})
 
     def add_order(self, field: str, direction: str) -> None:
         direction = direction.lower()