diff --git a/src/runtime/endpoints.rs b/src/runtime/endpoints.rs
index f3149c2a91f75540634698df841a26d35172af13..52f2cd4dfedffb4c27ab6c6bc5a12e3c63d0065c 100644
--- a/src/runtime/endpoints.rs
+++ b/src/runtime/endpoints.rs
@@ -234,10 +234,10 @@ impl EndpointManager {
             let recv_buffer = self.udp_in_buffer.as_mut_slice();
             while let Some(index) = self.udp_endpoint_store.polled_undrained.pop() {
                 let ee = &mut self.udp_endpoint_store.endpoint_exts[index];
-                if let Some(bytes_written) = ee.sock.recv(recv_buffer).ok() {
+                if let Some((bytes_written, from)) = ee.sock.recv_from(recv_buffer).ok() {
                     // I received a payload!
                     self.udp_endpoint_store.polled_undrained.insert(index);
-                    if !ee.received_this_round {
+                    if !ee.received_from_this_round.is_none() {
                         let payload = Payload::from(&recv_buffer[..bytes_written]);
                         let port_spec_var = port_info.spec_var_for(ee.getter_for_incoming);
                         let predicate = Predicate::singleton(port_spec_var, SpecVal::FIRING);
@@ -246,7 +246,7 @@ impl EndpointManager {
                             SendPayloadMsg { payload, predicate },
                         );
                         some_message_enqueued = true;
-                        ee.received_this_round = true;
+                        ee.received_from_this_round = Some(from);
                     } else {
                         // lose the message!
                     }
@@ -343,7 +343,7 @@ impl EndpointManager {
             self.udp_endpoint_store.endpoint_exts.len()
         );
         for ee in self.udp_endpoint_store.endpoint_exts.iter_mut() {
-            ee.received_this_round = false;
+            ee.received_from_this_round = None;
         }
     }
     pub(super) fn udp_endpoints_round_end(
@@ -351,6 +351,7 @@ impl EndpointManager {
         logger: &mut dyn Logger,
         decision: &Decision,
     ) -> Result<(), UnrecoverableSyncError> {
+        // retain received_from_this_round for use in pseudo_socket_api::recv_from
         log!(
             logger,
             "Ending round for {} udp endpoints",