diff --git a/migrations/mysql/2022-07-27-110000_add_group_support/up.sql b/migrations/mysql/2022-07-27-110000_add_group_support/up.sql
index b46dc0a8..3dde2e09 100644
--- a/migrations/mysql/2022-07-27-110000_add_group_support/up.sql
+++ b/migrations/mysql/2022-07-27-110000_add_group_support/up.sql
@@ -11,7 +11,7 @@ CREATE TABLE `groups` (
 CREATE TABLE groups_users (
   groups_uuid                       CHAR(36) NOT NULL REFERENCES `groups` (uuid),
   users_organizations_uuid          VARCHAR(36) NOT NULL REFERENCES users_organizations (uuid),
-  PRIMARY KEY (groups_uuid, users_organizations_uuid)
+  UNIQUE (groups_uuid, users_organizations_uuid)
 );
 
 CREATE TABLE collections_groups (
@@ -19,5 +19,5 @@ CREATE TABLE collections_groups (
   groups_uuid                       CHAR(36) NOT NULL REFERENCES `groups` (uuid),
   read_only                         BOOLEAN NOT NULL,
   hide_passwords                    BOOLEAN NOT NULL,
-  PRIMARY KEY (collections_uuid, groups_uuid)
+  UNIQUE (collections_uuid, groups_uuid)
 );
diff --git a/migrations/mysql/2026-03-22-100000_add_primary_keys_to_group_tables/down.sql b/migrations/mysql/2026-03-22-100000_add_primary_keys_to_group_tables/down.sql
new file mode 100644
index 00000000..f7f7e54a
--- /dev/null
+++ b/migrations/mysql/2026-03-22-100000_add_primary_keys_to_group_tables/down.sql
@@ -0,0 +1,7 @@
+ALTER TABLE groups_users
+  DROP PRIMARY KEY,
+  ADD UNIQUE (groups_uuid, users_organizations_uuid);
+
+ALTER TABLE collections_groups
+  DROP PRIMARY KEY,
+  ADD UNIQUE (collections_uuid, groups_uuid);
diff --git a/migrations/mysql/2026-03-22-100000_add_primary_keys_to_group_tables/up.sql b/migrations/mysql/2026-03-22-100000_add_primary_keys_to_group_tables/up.sql
new file mode 100644
index 00000000..c40f9d3d
--- /dev/null
+++ b/migrations/mysql/2026-03-22-100000_add_primary_keys_to_group_tables/up.sql
@@ -0,0 +1,10 @@
+-- groups_users and collections_groups were created with UNIQUE instead of
+-- PRIMARY KEY. Diesel requires primary keys on all tables for schema
+-- introspection. Drop the auto-named unique index and add the primary key.
+ALTER TABLE groups_users
+  DROP INDEX groups_uuid,
+  ADD PRIMARY KEY (groups_uuid, users_organizations_uuid);
+
+ALTER TABLE collections_groups
+  DROP INDEX collections_uuid,
+  ADD PRIMARY KEY (collections_uuid, groups_uuid);