diff --git a/src/runtime2/mod.rs b/src/runtime2/mod.rs
index 800fdf37cab02cfb191f2ec5a12d1422e237f9ed..af4373aca8c049f02a7d7bb0d07ba639819c9714 100644
--- a/src/runtime2/mod.rs
+++ b/src/runtime2/mod.rs
@@ -389,6 +389,7 @@ impl ConnectorStore {
     /// Retrieves public part of connector - accessible by many threads at once.
     fn get_public(&self, id: ConnectorId) -> &'static ConnectorPublic {
         unsafe {
+            debug_assert!(!self.free.contains(&(id.0 as usize)));
             let connector = self.connectors.get(id.0 as usize);
             debug_assert!(!connector.is_null());
             return &(**connector).public;
@@ -399,6 +400,7 @@ impl ConnectorStore {
     /// time.
     fn get_private(&self, key: &ConnectorKey) -> &'static mut ScheduledConnector {
         unsafe {
+            debug_assert!(!self.free.contains(&(key.index as usize)));
             let connector = self.connectors.get_mut(key.index as usize);
             debug_assert!(!connector.is_null());
             return &mut (**connector);