diff --git a/schema.sql b/schema.sql
index f4a05d1..81a5fd9 100644
--- a/schema.sql
+++ b/schema.sql
@@ -49,7 +49,7 @@ CREATE TABLE IF NOT EXISTS icons (
     key text,
 
     -- sha256 of the icon
-    hash text,
+    hash text UNIQUE,
 
     -- icon mime
     mime text NOT NULL,