diff --git a/tables.sql b/tables.sql
index 08dcb99..a885631 100644
--- a/tables.sql
+++ b/tables.sql
@@ -4,7 +4,7 @@ DROP TABLE IF EXISTS accounts;
 
 CREATE TABLE accounts (
     actor_type VARCHAR(1000) NOT NULL,
-    id VARCHAR(2083) NOT NULL PRIMARY KEY,
+    id VARCHAR(2083) NOT NULL PRIMARY KEY UNIQUE,
     inbox VARCHAR(2083) NOT NULL,
     outbox VARCHAR(2083) NOT NULL,
     followers VARCHAR(2083) NOT NULL,
@@ -21,7 +21,7 @@ CREATE TABLE accounts (
 );
 
 CREATE TABLE posts (
-    id VARCHAR(2083) NOT NULL,
+    id VARCHAR(2083) NOT NULL PRIMARY KEY UNIQUE,
     inreplyto VARCHAR(2083),
     published TIMESTAMP with time zone NOT NULL,
     summary TEXT,
@@ -34,7 +34,7 @@ CREATE TABLE posts (
 );
 
 CREATE TABLE instances (
-    endpoint VARCHAR(2083) NOT NULL,
+    endpoint VARCHAR(2083) NOT NULL PRIMARY KEY UNIQUE,
     autostart BOOLEAN,
     state VARCHAR(16),
     username VARCHAR(32),