diff --git a/src/test/connector.rs b/src/test/connector.rs
index dd2a974d7d461b9da08714d7b38bd060559cdee7..7568053d6f051a511abc2e0e9b4151a8d330d8ad 100644
--- a/src/test/connector.rs
+++ b/src/test/connector.rs
@@ -9,6 +9,7 @@ use test_generator::test_resources;
 
 use crate::common::*;
 use crate::runtime::*;
+use crate::runtime::errors::*;
 
 #[test]
 fn incremental() {
@@ -50,7 +51,7 @@ fn incremental() {
 }
 
 #[test]
-fn duo() {
+fn duo_positive() {
     let timeout = Duration::from_millis(1_500);
     let addrs = ["127.0.0.1:7012".parse().unwrap(), "127.0.0.1:7013".parse().unwrap()];
     let a = thread::spawn(move || {
@@ -104,3 +105,56 @@ fn duo() {
     handle(a.join());
     handle(b.join());
 }
+
+#[test]
+fn duo_negative() {
+    let timeout = Duration::from_millis(500);
+    let addrs = ["127.0.0.1:7012".parse().unwrap(), "127.0.0.1:7013".parse().unwrap()];
+    let a = thread::spawn(move || {
+        let mut x = Connector::Unconfigured(Unconfigured { controller_id: 0 });
+        x.configure(b"
+        primitive main(out a, out b) {
+            synchronous {}
+            synchronous {
+                msg m = create(0);
+                put(a, m); // fires a on second round
+            }
+        }").unwrap();
+        x.bind_port(0, PortBinding::Passive(addrs[0])).unwrap();
+        x.bind_port(1, PortBinding::Passive(addrs[1])).unwrap();
+        x.connect(timeout).unwrap();
+        assert_eq!(0, x.sync(timeout).unwrap());
+        match x.sync(timeout) {
+            Err(SyncErr::Timeout) => {}
+            x => unreachable!("{:?}", x)
+        }
+    });
+    let b = thread::spawn(move || {
+        let mut x = Connector::Unconfigured(Unconfigured { controller_id: 1 });
+        x.configure(b"
+        primitive main(in a, in b) {
+            while (true) {
+                synchronous {
+                    if (fires(a)) {
+                        get(a);
+                    }
+                }
+                synchronous {
+                    if (fires(b)) { // never fire a on even round
+                        get(b);
+                    }
+                }
+            }
+        }").unwrap();
+        x.bind_port(0, PortBinding::Active(addrs[0])).unwrap();
+        x.bind_port(1, PortBinding::Active(addrs[1])).unwrap();
+        x.connect(timeout).unwrap();
+        assert_eq!(0, x.sync(timeout).unwrap());
+        match x.sync(timeout) {
+            Err(SyncErr::Timeout) => {}
+            x => unreachable!("{:?}", x)
+        }
+    });
+    handle(a.join());
+    handle(b.join());
+}