diff --git a/openmls/src/framing/mls_content.rs b/openmls/src/framing/mls_content.rs
index 5bc9e75a22..2cf35d8e26 100644
--- a/openmls/src/framing/mls_content.rs
+++ b/openmls/src/framing/mls_content.rs
@@ -227,7 +227,8 @@ pub(crate) fn framed_content_tbs_serialized<'context, W: Write>(
     // NewMemberCommit.
     written += match serialized_context.into() {
         Some(context) if matches!(sender, Sender::Member(_) | Sender::NewMemberCommit) => {
-            writer.write(context)?
+            writer.write_all(context)?;
+            context.len()
         }
         _ => 0,
     };
diff --git a/openmls/src/group/core_group/new_from_welcome.rs b/openmls/src/group/core_group/new_from_welcome.rs
index 08e5b4b272..d2d98de122 100644
--- a/openmls/src/group/core_group/new_from_welcome.rs
+++ b/openmls/src/group/core_group/new_from_welcome.rs
@@ -316,7 +316,7 @@ mod tests {
     fn psk_ids_should_be_valid() {
         let group_id = GroupId::from_slice(b"test");
         let epoch = GroupEpoch(1);
-        let psks = vec![
+        let psks = [
             ResumptionPsk::new(ResumptionPskUsage::Reinit, group_id.clone(), epoch),
             ResumptionPsk::new(ResumptionPskUsage::Branch, group_id.clone(), epoch),
             ResumptionPsk::new(ResumptionPskUsage::Application, group_id, epoch),
@@ -328,7 +328,7 @@ mod tests {
     fn psk_ids_should_be_valid_application() {
         let group_id = GroupId::from_slice(b"test");
         let epoch = GroupEpoch(1);
-        let psks = vec![
+        let psks = [
             ResumptionPsk::new(ResumptionPskUsage::Application, group_id.clone(), epoch),
             ResumptionPsk::new(ResumptionPskUsage::Application, group_id.clone(), epoch),
             ResumptionPsk::new(ResumptionPskUsage::Application, group_id.clone(), epoch),
@@ -341,7 +341,7 @@ mod tests {
     fn psk_ids_should_be_invalid_reinit() {
         let group_id = GroupId::from_slice(b"test");
         let epoch = GroupEpoch(1);
-        let psks = vec![
+        let psks = [
             ResumptionPsk::new(ResumptionPskUsage::Reinit, group_id.clone(), epoch),
             ResumptionPsk::new(ResumptionPskUsage::Branch, group_id.clone(), epoch),
             ResumptionPsk::new(ResumptionPskUsage::Reinit, group_id.clone(), epoch),
@@ -357,7 +357,7 @@ mod tests {
     fn psk_ids_should_be_invalid_branch() {
         let group_id = GroupId::from_slice(b"test");
         let epoch = GroupEpoch(1);
-        let psks = vec![
+        let psks = [
             ResumptionPsk::new(ResumptionPskUsage::Reinit, group_id.clone(), epoch),
             ResumptionPsk::new(ResumptionPskUsage::Branch, group_id.clone(), epoch),
             ResumptionPsk::new(ResumptionPskUsage::Branch, group_id.clone(), epoch),
@@ -373,7 +373,7 @@ mod tests {
     fn psk_ids_should_be_invalid() {
         let group_id = GroupId::from_slice(b"test");
         let epoch = GroupEpoch(1);
-        let psks = vec![
+        let psks = [
             ResumptionPsk::new(ResumptionPskUsage::Reinit, group_id.clone(), epoch),
             ResumptionPsk::new(ResumptionPskUsage::Branch, group_id.clone(), epoch),
             ResumptionPsk::new(ResumptionPskUsage::Reinit, group_id.clone(), epoch),