diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8ace2d3..c3f37a6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 ### Changed
 
 - Increase maximum number of custom emojis per post to 50.
+- Validate actor aliases before saving into database.
 
 ## [1.19.1] - 2023-03-31
 
diff --git a/src/activitypub/actors/helpers.rs b/src/activitypub/actors/helpers.rs
index 41a93ba..5f9849f 100644
--- a/src/activitypub/actors/helpers.rs
+++ b/src/activitypub/actors/helpers.rs
@@ -18,6 +18,7 @@ use crate::activitypub::{
     actors::types::Actor,
     fetcher::fetchers::fetch_file,
     handlers::create::handle_emoji,
+    identifiers::validate_object_id,
     receiver::{parse_array, HandlerError},
     vocabulary::{EMOJI, HASHTAG},
 };
@@ -92,7 +93,17 @@ fn parse_aliases(actor: &Actor) -> Vec<String> {
     actor.also_known_as.as_ref()
         .and_then(|value| {
             match parse_array(value) {
-                Ok(array) => Some(array),
+                Ok(array) => {
+                    let mut aliases = vec![];
+                    for actor_id in array {
+                        if validate_object_id(&actor_id).is_err() {
+                            log::warn!("invalid alias: {}", actor_id);
+                            continue;
+                        };
+                        aliases.push(actor_id);
+                    };
+                    Some(aliases)
+                },
                 Err(_) => {
                     log::warn!("invalid alias list: {}", value);
                     None
diff --git a/src/activitypub/identifiers.rs b/src/activitypub/identifiers.rs
index 5b650a9..e9cdf55 100644
--- a/src/activitypub/identifiers.rs
+++ b/src/activitypub/identifiers.rs
@@ -5,6 +5,7 @@ use mitra_models::{
     posts::types::Post,
     profiles::types::DbActorProfile,
 };
+use mitra_utils::urls::get_hostname;
 
 use crate::errors::ValidationError;
 
@@ -81,6 +82,12 @@ pub fn local_tag_collection(instance_url: &str, tag_name: &str) -> String {
     format!("{}/collections/tags/{}", instance_url, tag_name)
 }
 
+pub fn validate_object_id(object_id: &str) -> Result<(), ValidationError> {
+    get_hostname(object_id)
+        .map_err(|_| ValidationError("invalid object ID"))?;
+    Ok(())
+}
+
 pub fn parse_local_actor_id(
     instance_url: &str,
     actor_id: &str,