diff --git a/Cargo.lock b/Cargo.lock
index ba19a1961..73aa51ef9 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -10,9 +10,9 @@ checksum = "fe438c63458706e03479442743baae6c88256498e6431708f6dfc520a26515d3"
 
 [[package]]
 name = "activitypub_federation"
-version = "0.5.0"
+version = "0.5.1-beta.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8bac58c1d61b6e2358adbd043c78ba853428102b489acb7b6cb74ee6f2ae668f"
+checksum = "866db431760d14a7360f12e75ad48f3265b5b89cd2303e548a02bcc8983e4fcd"
 dependencies = [
  "activitystreams-kinds",
  "actix-web",
diff --git a/Cargo.toml b/Cargo.toml
index c54255e41..bfb275b37 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -95,7 +95,7 @@ lemmy_routes = { version = "=0.19.2-rc.2", path = "./crates/routes" }
 lemmy_db_views = { version = "=0.19.2-rc.2", path = "./crates/db_views" }
 lemmy_db_views_actor = { version = "=0.19.2-rc.2", path = "./crates/db_views_actor" }
 lemmy_db_views_moderator = { version = "=0.19.2-rc.2", path = "./crates/db_views_moderator" }
-activitypub_federation = { version = "0.5.0", default-features = false, features = [
+activitypub_federation = { version = "0.5.1-beta.1", default-features = false, features = [
   "actix-web",
 ] }
 diesel = "2.1.4"
diff --git a/crates/apub/assets/mastodon/activities/flag.json b/crates/apub/assets/mastodon/activities/flag.json
new file mode 100644
index 000000000..83f4c0817
--- /dev/null
+++ b/crates/apub/assets/mastodon/activities/flag.json
@@ -0,0 +1,13 @@
+{
+  "@context": "https://www.w3.org/ns/activitystreams",
+  "id": "https://mastodon.example/ccb4f39a-506a-490e-9a8c-71831c7713a4",
+  "type": "Flag",
+  "actor": "https://mastodon.example/actor",
+  "content": "Please take a look at this user and their posts",
+  "object": [
+    "https://example.com/users/1",
+    "https://example.com/posts/380590",
+    "https://example.com/posts/380591"
+  ],
+  "to": "https://example.com/users/1"
+}
diff --git a/crates/apub/assets/mbin/activities/accept.json b/crates/apub/assets/mbin/activities/accept.json
new file mode 100644
index 000000000..3a190977c
--- /dev/null
+++ b/crates/apub/assets/mbin/activities/accept.json
@@ -0,0 +1,12 @@
+{
+  "@context": "https://www.w3.org/ns/activitystreams",
+  "id": "https://some-mbin.instance/f/object/2721ffc3-f8a9-417e-a124-af057434a3af#accept",
+  "type": "Accept",
+  "actor": "https://some-mbin.instance/m/someMag",
+  "object": {
+    "id": "https://some-other.instance/f/object/c51ea652-e594-4920-a989-f5350f0cec05",
+    "type": "Follow",
+    "actor": "https://some-other.instance/u/someUser",
+    "object": "https://some-mbin.instance/m/someMag"
+  }
+}
diff --git a/crates/apub/assets/mbin/activities/flag.json b/crates/apub/assets/mbin/activities/flag.json
new file mode 100644
index 000000000..7c1e5ae23
--- /dev/null
+++ b/crates/apub/assets/mbin/activities/flag.json
@@ -0,0 +1,11 @@
+{
+  "@context": ["https://www.w3.org/ns/activitystreams"],
+  "id": "https://mbin-test1/reports/45f8a01d-a73e-4575-bffa-c9f24c61f458",
+  "type": "Flag",
+  "actor": "https://mbin-test1/u/BentiGorlich",
+  "object": ["https://lemmy-test/post/4", "https://lemmy-test/u/BentiGorlich"],
+  "audience": "https://lemmy-test/c/test_mag",
+  "summary": "dikjhgasdpas dsaü",
+  "content": "dikjhgasdpas dsaü",
+  "to": ["https://lemmy-test/c/test_mag"]
+}
diff --git a/crates/apub/src/activities/community/report.rs b/crates/apub/src/activities/community/report.rs
index 974810f61..70278075c 100644
--- a/crates/apub/src/activities/community/report.rs
+++ b/crates/apub/src/activities/community/report.rs
@@ -2,7 +2,10 @@ use crate::{
   activities::{generate_activity_id, send_lemmy_activity, verify_person_in_community},
   insert_received_activity,
   objects::{community::ApubCommunity, instance::ApubSite, person::ApubPerson},
-  protocol::{activities::community::report::Report, InCommunity},
+  protocol::{
+    activities::community::report::{Report, ReportObject},
+    InCommunity,
+  },
   PostOrComment,
 };
 use activitypub_federation::{
@@ -45,8 +48,9 @@ impl Report {
     let report = Report {
       actor: actor.id().into(),
       to: [community.id().into()],
-      object: object_id.clone(),
-      summary: reason,
+      object: ReportObject::Lemmy(object_id.clone()),
+      summary: Some(reason),
+      content: None,
       kind,
       id: id.clone(),
       audience: Some(community.id().into()),
@@ -97,6 +101,7 @@ impl ActivityHandler for Report {
   #[tracing::instrument(skip_all)]
   async fn receive(self, context: &Data<Self::DataType>) -> Result<(), LemmyError> {
     let actor = self.actor.dereference(context).await?;
+    let reason = self.reason()?;
     match self.object.dereference(context).await? {
       PostOrComment::Post(post) => {
         let report_form = PostReportForm {
@@ -104,7 +109,7 @@ impl ActivityHandler for Report {
           post_id: post.id,
           original_post_name: post.name.clone(),
           original_post_url: post.url.clone(),
-          reason: self.summary.clone(),
+          reason,
           original_post_body: post.body.clone(),
         };
         PostReport::report(&mut context.pool(), &report_form).await?;
@@ -114,7 +119,7 @@ impl ActivityHandler for Report {
           creator_id: actor.id,
           comment_id: comment.id,
           original_comment_text: comment.content.clone(),
-          reason: self.summary.clone(),
+          reason,
         };
         CommentReport::report(&mut context.pool(), &report_form).await?;
       }
diff --git a/crates/apub/src/protocol/activities/community/report.rs b/crates/apub/src/protocol/activities/community/report.rs
index 6e8a1bbf3..adcddfdfc 100644
--- a/crates/apub/src/protocol/activities/community/report.rs
+++ b/crates/apub/src/protocol/activities/community/report.rs
@@ -11,7 +11,7 @@ use activitypub_federation::{
   protocol::helpers::deserialize_one,
 };
 use lemmy_api_common::context::LemmyContext;
-use lemmy_utils::error::LemmyError;
+use lemmy_utils::error::{LemmyError, LemmyErrorType, LemmyResult};
 use serde::{Deserialize, Serialize};
 use url::Url;
 
@@ -21,14 +21,54 @@ pub struct Report {
   pub(crate) actor: ObjectId<ApubPerson>,
   #[serde(deserialize_with = "deserialize_one")]
   pub(crate) to: [ObjectId<ApubCommunity>; 1],
-  pub(crate) object: ObjectId<PostOrComment>,
-  pub(crate) summary: String,
+  pub(crate) object: ReportObject,
+  /// Report reason as sent by Lemmy
+  pub(crate) summary: Option<String>,
+  /// Report reason as sent by Mastodon
+  pub(crate) content: Option<String>,
   #[serde(rename = "type")]
   pub(crate) kind: FlagType,
   pub(crate) id: Url,
   pub(crate) audience: Option<ObjectId<ApubCommunity>>,
 }
 
+impl Report {
+  pub fn reason(&self) -> LemmyResult<String> {
+    self
+      .summary
+      .clone()
+      .or(self.content.clone())
+      .ok_or(LemmyErrorType::CouldntFindObject.into())
+  }
+}
+
+#[derive(Clone, Debug, Deserialize, Serialize)]
+#[serde(untagged)]
+pub(crate) enum ReportObject {
+  Lemmy(ObjectId<PostOrComment>),
+  /// Mastodon sends an array containing user id and one or more post ids
+  Mastodon(Vec<Url>),
+}
+
+impl ReportObject {
+  pub async fn dereference(self, context: &Data<LemmyContext>) -> LemmyResult<PostOrComment> {
+    match self {
+      ReportObject::Lemmy(l) => l.dereference(context).await,
+      ReportObject::Mastodon(objects) => {
+        for o in objects {
+          // Find the first reported item which can be dereferenced as post or comment (Lemmy can
+          // only handle one item per report).
+          let deref = ObjectId::from(o).dereference(context).await;
+          if deref.is_ok() {
+            return deref;
+          }
+        }
+        Err(LemmyErrorType::CouldntFindObject.into())
+      }
+    }
+  }
+}
+
 #[async_trait::async_trait]
 impl InCommunity for Report {
   async fn community(&self, context: &Data<LemmyContext>) -> Result<ApubCommunity, LemmyError> {
diff --git a/crates/apub/src/protocol/activities/mod.rs b/crates/apub/src/protocol/activities/mod.rs
index e7c5f64d0..024f08929 100644
--- a/crates/apub/src/protocol/activities/mod.rs
+++ b/crates/apub/src/protocol/activities/mod.rs
@@ -18,10 +18,10 @@ pub enum CreateOrUpdateType {
 mod tests {
   use crate::protocol::{
     activities::{
-      community::announce::AnnounceActivity,
+      community::{announce::AnnounceActivity, report::Report},
       create_or_update::{note::CreateOrUpdateNote, page::CreateOrUpdatePage},
       deletion::delete::Delete,
-      following::{follow::Follow, undo_follow::UndoFollow},
+      following::{accept::AcceptFollow, follow::Follow, undo_follow::UndoFollow},
       voting::{undo_vote::UndoVote, vote::Vote},
     },
     tests::test_json,
@@ -50,6 +50,7 @@ mod tests {
     test_json::<UndoFollow>("assets/mastodon/activities/undo_follow.json")?;
     test_json::<Vote>("assets/mastodon/activities/like_page.json")?;
     test_json::<UndoVote>("assets/mastodon/activities/undo_like_page.json")?;
+    test_json::<Report>("assets/mastodon/activities/flag.json")?;
     Ok(())
   }
 
@@ -88,4 +89,11 @@ mod tests {
     test_json::<AnnounceActivity>("assets/peertube/activities/announce_video.json")?;
     Ok(())
   }
+
+  #[test]
+  fn test_parse_mbin_activities() -> LemmyResult<()> {
+    test_json::<AcceptFollow>("assets/mbin/activities/accept.json")?;
+    test_json::<Report>("assets/mbin/activities/flag.json")?;
+    Ok(())
+  }
 }