diff --git a/crates/net/src/connection/delivery/mod.rs b/crates/net/src/connection/delivery/mod.rs
index 0c7526626..71fc34f2e 100644
--- a/crates/net/src/connection/delivery/mod.rs
+++ b/crates/net/src/connection/delivery/mod.rs
@@ -13,7 +13,7 @@ use self::{
     received::{IdContinuity, Received},
 };
 use super::book::{Connection, ConnectionBook};
-use crate::{record::DeliveryRecord, tasks::OutDatagram, Reliability};
+use crate::{record::DeliveryRecord, tasks::OutDatagram, Reliability, MAX_PACKAGE_SIZE};
 
 mod confirms;
 mod deliveries;
@@ -129,14 +129,18 @@ impl ConnDeliveryHandler {
     ///
     /// # Panics
     ///
-    /// Panics if `buf` len is smaller than length of any of the drained
-    /// buffered pending package.
+    /// * If `buf` len is smaller than length of any of the drained buffered
+    ///   pending package.
+    ///
+    /// * If `data` is longer than [`MAX_PACKAGE_SIZE`].
     fn push<'b>(
         &mut self,
         record: DeliveryRecord,
         data: Vec<u8>,
         buf: &'b mut [u8],
     ) -> Result<Deliveries<'_, 'b>, ReceivedIdError> {
+        assert!(data.len() <= MAX_PACKAGE_SIZE);
+
         let result = self.received.process(record.header().id());
         if let Ok(_) | Err(ReceivedIdError::Duplicate) = result {
             // Push to the buffer even duplicate packages, because the reason
diff --git a/crates/net/src/connection/delivery/pending.rs b/crates/net/src/connection/delivery/pending.rs
index 3865f5cd4..20739bec8 100644
--- a/crates/net/src/connection/delivery/pending.rs
+++ b/crates/net/src/connection/delivery/pending.rs
@@ -1,6 +1,8 @@
 use std::collections::BTreeMap;
 
-use crate::{connection::databuf::DataBuf, header::PackageId, record::DeliveryRecord};
+use crate::{
+    connection::databuf::DataBuf, header::PackageId, record::DeliveryRecord, MAX_PACKAGE_SIZE,
+};
 
 /// Buffer for packages received out-of-order and thus awaiting the right
 /// moment to be delivered.
@@ -24,8 +26,11 @@ impl Pending {
     /// * When there already is a pending package with the given `id`.
     ///
     /// * It is not a (semi-)ordered package.
+    ///
+    /// * If the data is longer than [`MAX_PACKAGE_SIZE`].
     pub(super) fn store(&mut self, record: DeliveryRecord, data: &[u8]) {
         assert!(record.header().reliability().is_ordered());
+        assert!(data.len() <= MAX_PACKAGE_SIZE);
         let id = record.header().id();
         let result = self.ids.insert(id, record);
         assert!(result.is_none());
diff --git a/crates/net/src/connection/dispatch/mod.rs b/crates/net/src/connection/dispatch/mod.rs
index 881dd194f..29bfe5077 100644
--- a/crates/net/src/connection/dispatch/mod.rs
+++ b/crates/net/src/connection/dispatch/mod.rs
@@ -13,6 +13,7 @@ use super::book::{Connection, ConnectionBook};
 use crate::{
     header::{DatagramHeader, PackageHeader, PackageId, PackageIdRange},
     tasks::OutDatagram,
+    MAX_PACKAGE_SIZE,
 };
 
 mod resends;
@@ -39,6 +40,11 @@ impl DispatchHandler {
         handler.next_package_id()
     }
 
+    /// # Panics
+    ///
+    /// * If the package is already registered as sent.
+    ///
+    /// * If the data are longer than [`MAX_PACKAGE_SIZE`].
     pub(crate) async fn sent(
         &mut self,
         time: Instant,
@@ -46,6 +52,7 @@ impl DispatchHandler {
         header: PackageHeader,
         data: &[u8],
     ) {
+        assert!(data.len() <= MAX_PACKAGE_SIZE);
         let mut book = self.book.lock().await;
         let handler = book.update(time, addr, ConnDispatchHandler::new);
         handler.resends.push(header, data, time);
diff --git a/crates/net/src/connection/dispatch/resends.rs b/crates/net/src/connection/dispatch/resends.rs
index a9efd1b86..99f6d0337 100644
--- a/crates/net/src/connection/dispatch/resends.rs
+++ b/crates/net/src/connection/dispatch/resends.rs
@@ -9,6 +9,7 @@ use priority_queue::PriorityQueue;
 use crate::{
     connection::{book::MAX_CONN_AGE, databuf::DataBuf},
     header::{PackageHeader, PackageId},
+    MAX_PACKAGE_SIZE,
 };
 
 pub(super) const START_BACKOFF_MS: u64 = 220;
@@ -43,8 +44,16 @@ impl Resends {
     }
 
     /// Registers new package for re-sending until it is resolved.
+    ///
+    /// # Panics
+    ///
+    /// * If the package (ID) is already stored.
+    ///
+    /// * If data is longer than [`MAX_PACKAGE_SIZE`].
     pub(super) fn push(&mut self, header: PackageHeader, data: &[u8], now: Instant) {
-        self.queue.push(header.id(), Timing::new(now));
+        assert!(data.len() <= MAX_PACKAGE_SIZE);
+        let result = self.queue.push(header.id(), Timing::new(now));
+        assert!(result.is_none());
         self.headers.insert(header.id(), header);
         self.data.push(header.id(), data);
     }
diff --git a/crates/net/src/tasks/dreceiver.rs b/crates/net/src/tasks/dreceiver.rs
index 4f38fc2bc..a56aaae87 100644
--- a/crates/net/src/tasks/dreceiver.rs
+++ b/crates/net/src/tasks/dreceiver.rs
@@ -6,7 +6,7 @@ use tracing::{error, info, warn};
 use crate::{
     header::{DatagramHeader, PackageHeader},
     protocol::{MsgRecvError, ProtocolSocket},
-    MAX_DATAGRAM_SIZE,
+    MAX_DATAGRAM_SIZE, MAX_PACKAGE_SIZE,
 };
 
 pub(super) struct InSystemDatagram {
@@ -54,6 +54,8 @@ pub(super) async fn run(
             }
         };
 
+        assert!(data.len() <= MAX_PACKAGE_SIZE);
+
         // Closed channel(s) are handled at the top part of the loop,
         // therefore errors from .send() are not treated below.
         match header {