diff --git a/comments/sql/migrate.001.sql b/comments/sql/migrate.001.sql
index e6c855dd28ccd5b9ac935949bb26a6c3beaee03d..ef8d8b5795aeaaa1102d464318cded94c6db8bf5 100644
--- a/comments/sql/migrate.001.sql
+++ b/comments/sql/migrate.001.sql
@@ -80,3 +80,10 @@ FOR EACH ROW
     UPDATE comments
     SET tags = (SELECT tagstring FROM concatenated_tags ctags WHERE ctags.comment_id = comments.id)
     WHERE id = OLD.comment_id;
+
+
+-- Remove unused target types
+
+DELETE FROM targets WHERE type = 'unknown' OR type = 'challenge';
+
+ALTER TABLE targets MODIFY COLUMN type ENUM('class', 'guide', 'video') NOT NULL DEFAULT 'class';
diff --git a/comments/sql/schema.sql b/comments/sql/schema.sql
index b7bfd3a9b003ac4d9df6aa03b091135552e867b5..a4f8d84febe6c6bcb7e74f960051111e72c12d17 100644
--- a/comments/sql/schema.sql
+++ b/comments/sql/schema.sql
@@ -19,7 +19,7 @@ CREATE TABLE users (
 CREATE TABLE targets (
     id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
     domain VARCHAR(50) NOT NULL, -- combines sdk & version
-    type ENUM('class', 'guide', 'video', 'unknown', 'challenge') NOT NULL DEFAULT 'class',
+    type ENUM('class', 'guide', 'video') NOT NULL DEFAULT 'class',
     cls VARCHAR(100) NOT NULL,    -- "Ext.draw.Sprite"
     member VARCHAR(100) NOT NULL, -- "method-setAttributes"
     -- the whole target must be unique