diff --git a/src/models/users/queries.rs b/src/models/users/queries.rs
index 9110946..41f45f0 100644
--- a/src/models/users/queries.rs
+++ b/src/models/users/queries.rs
@@ -60,6 +60,23 @@ pub async fn create_user(
     user_data: UserCreateData,
 ) -> Result<User, DatabaseError> {
     let transaction = db_client.transaction().await?;
+    // Prevent changes to actor_profile table
+    transaction.execute(
+        "LOCK TABLE actor_profile IN EXCLUSIVE MODE",
+        &[],
+    ).await?;
+    // Ensure there are no local accounts with a similar name
+    let maybe_row = transaction.query_opt(
+        "
+        SELECT 1
+        FROM user_account JOIN actor_profile USING (id)
+        WHERE actor_profile.username ILIKE $1
+        ",
+        &[&user_data.username],
+    ).await?;
+    if maybe_row.is_some() {
+        return Err(DatabaseError::AlreadyExists("user"));
+    };
     // Use invite code
     if let Some(ref invite_code) = user_data.invite_code {
         let updated_count = transaction.execute(
@@ -72,8 +89,8 @@ pub async fn create_user(
         ).await?;
         if updated_count == 0 {
             return Err(DatabaseError::NotFound("invite code"));
-        }
-    }
+        };
+    };
     // Create profile
     let profile_data = ProfileCreateData {
         username: user_data.username.clone(),
@@ -245,3 +262,27 @@ pub async fn get_user_count(
     let count = row.try_get("count")?;
     Ok(count)
 }
+
+#[cfg(test)]
+mod tests {
+    use serial_test::serial;
+    use crate::database::test_utils::create_test_database;
+    use super::*;
+
+    #[tokio::test]
+    #[serial]
+    async fn test_create_user_impersonation_protection() {
+        let db_client = &mut create_test_database().await;
+        let user_data = UserCreateData {
+            username: "myname".to_string(),
+            ..Default::default()
+        };
+        create_user(db_client, user_data).await.unwrap();
+        let another_user_data = UserCreateData {
+            username: "myName".to_string(),
+            ..Default::default()
+        };
+        let result = create_user(db_client, another_user_data).await;
+        assert!(matches!(result, Err(DatabaseError::AlreadyExists("user"))));
+    }
+}