diff --git a/lib/pleroma/web/activity_pub/activity_pub.ex b/lib/pleroma/web/activity_pub/activity_pub.ex
index dcdc7085f..254d91a7e 100644
--- a/lib/pleroma/web/activity_pub/activity_pub.ex
+++ b/lib/pleroma/web/activity_pub/activity_pub.ex
@@ -1530,6 +1530,18 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
     # we request WebFinger here
     nickname = additional[:nickname_from_acct] || generate_nickname(data)
 
+    # also_known_as must be a URL
+    also_known_as =
+      data
+      |> Map.get("alsoKnownAs", [])
+      |> Enum.filter(fn url ->
+        case URI.parse(url) do
+          %URI{scheme: "http"} -> true
+          %URI{scheme: "https"} -> true
+          _ -> false
+        end
+      end)
+
     %{
       ap_id: data["id"],
       uri: get_actor_url(data["url"]),
@@ -1547,7 +1559,7 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
       featured_address: featured_address,
       bio: data["summary"] || "",
       actor_type: actor_type,
-      also_known_as: Map.get(data, "alsoKnownAs", []),
+      also_known_as: also_known_as,
       public_key: public_key,
       inbox: data["inbox"],
       shared_inbox: shared_inbox,
diff --git a/test/fixtures/microblogpub/user_with_invalid_also_known_as.json b/test/fixtures/microblogpub/user_with_invalid_also_known_as.json
new file mode 100644
index 000000000..a03076226
--- /dev/null
+++ b/test/fixtures/microblogpub/user_with_invalid_also_known_as.json
@@ -0,0 +1,57 @@
+{
+  "@context": [
+    "https://www.w3.org/ns/activitystreams",
+    "https://w3id.org/security/v1",
+    {
+      "Hashtag": "as:Hashtag",
+      "sensitive": "as:sensitive",
+      "manuallyApprovesFollowers": "as:manuallyApprovesFollowers",
+      "alsoKnownAs": {
+        "@id": "as:alsoKnownAs",
+        "@type": "@id"
+      },
+      "movedTo": {
+        "@id": "as:movedTo",
+        "@type": "@id"
+      },
+      "toot": "http://joinmastodon.org/ns#",
+      "featured": {
+        "@id": "toot:featured",
+        "@type": "@id"
+      },
+      "Emoji": "toot:Emoji",
+      "blurhash": "toot:blurhash",
+      "votersCount": "toot:votersCount",
+      "schema": "http://schema.org#",
+      "PropertyValue": "schema:PropertyValue",
+      "value": "schema:value",
+      "ostatus": "http://ostatus.org#",
+      "conversation": "ostatus:conversation"
+    }
+  ],
+  "type": "Person",
+  "id": "https://mbp.example.com",
+  "following": "https://mbp.example.com/following",
+  "followers": "https://mbp.example.com/followers",
+  "featured": "https://mbp.example.com/featured",
+  "inbox": "https://mbp.example.com/inbox",
+  "outbox": "https://mbp.example.com/outbox",
+  "preferredUsername": "MBP",
+  "name": "MBP",
+  "summary": "wowee",
+  "endpoints": {
+    "sharedInbox": "https://mbp.example.com/inbox"
+  },
+  "url": "https://mbp.example.com/",
+  "manuallyApprovesFollowers": false,
+  "attachment": [],
+  "icon": {
+    "mediaType": "image/jpeg",
+    "type": "Image",
+    "url": "https://beta.4201337.xyz/static/denise.jpg"
+  },
+  "tag": [],
+  "alsoKnownAs": [
+    "example@elsewhere.com"
+  ]
+}
diff --git a/test/pleroma/user_test.exs b/test/pleroma/user_test.exs
index 195df2a03..b67aa48bb 100644
--- a/test/pleroma/user_test.exs
+++ b/test/pleroma/user_test.exs
@@ -968,6 +968,24 @@ defmodule Pleroma.UserTest do
 
       assert user.last_refreshed_at == orig_user.last_refreshed_at
     end
+
+    test "it doesn't fail on invalid alsoKnownAs entries" do
+      Tesla.Mock.mock(fn
+        %{url: "https://mbp.example.com/"} ->
+          %Tesla.Env{
+            status: 200,
+            body:
+              "test/fixtures/microblogpub/user_with_invalid_also_known_as.json"
+              |> File.read!(),
+            headers: [{"content-type", "application/activity+json"}]
+          }
+
+        _ ->
+          %Tesla.Env{status: 404}
+      end)
+
+      assert {:ok, %User{also_known_as: []}} = User.get_or_fetch_by_ap_id("https://mbp.example.com/")
+    end
   end
 
   test "returns an ap_id for a user" do