diff --git a/datafusion/proto/src/physical_plan/mod.rs b/datafusion/proto/src/physical_plan/mod.rs
index 504aa0672911..fda2395c98b8 100644
--- a/datafusion/proto/src/physical_plan/mod.rs
+++ b/datafusion/proto/src/physical_plan/mod.rs
@@ -506,7 +506,7 @@ impl AsExecutionPlan for protobuf::PhysicalPlanNode {
                                             let sort_exprs = &[];
                                             let ordering_req = &[];
                                             let ignore_nulls = false;
-                                            udaf::create_aggregate_expr(agg_udf.as_ref(), &input_phy_expr, logical_exprs, sort_exprs, ordering_req, &physical_schema, name, ignore_nulls, false)
+                                            udaf::create_aggregate_expr(agg_udf.as_ref(), &input_phy_expr, logical_exprs, sort_exprs, ordering_req, &physical_schema, name, ignore_nulls, agg_node.distinct)
                                         }
                                     }
                                 }).transpose()?.ok_or_else(|| {
diff --git a/datafusion/proto/src/physical_plan/to_proto.rs b/datafusion/proto/src/physical_plan/to_proto.rs
index 5e982ad2afde..28ee44d33b8c 100644
--- a/datafusion/proto/src/physical_plan/to_proto.rs
+++ b/datafusion/proto/src/physical_plan/to_proto.rs
@@ -64,7 +64,7 @@ pub fn serialize_physical_aggr_expr(
                     aggregate_function: Some(physical_aggregate_expr_node::AggregateFunction::UserDefinedAggrFunction(name)),
                     expr: expressions,
                     ordering_req,
-                    distinct: false,
+                    distinct: a.is_distinct(),
                 },
             )),
         });