diff --git a/modules/common/src/main/scala/docspell/common/IdRef.scala b/modules/common/src/main/scala/docspell/common/IdRef.scala
index 8c32405c..918030e7 100644
--- a/modules/common/src/main/scala/docspell/common/IdRef.scala
+++ b/modules/common/src/main/scala/docspell/common/IdRef.scala
@@ -1,5 +1,7 @@
 package docspell.common
 
+import cats.Order
+
 import io.circe._
 import io.circe.generic.semiauto._
 
@@ -11,4 +13,7 @@ object IdRef {
     deriveEncoder[IdRef]
   implicit val jsonDecoder: Decoder[IdRef] =
     deriveDecoder[IdRef]
+
+  implicit val order: Order[IdRef] =
+    Order.by(_.id)
 }
diff --git a/modules/common/src/main/scala/docspell/common/Ident.scala b/modules/common/src/main/scala/docspell/common/Ident.scala
index dcb8cf2d..95e58bc6 100644
--- a/modules/common/src/main/scala/docspell/common/Ident.scala
+++ b/modules/common/src/main/scala/docspell/common/Ident.scala
@@ -6,6 +6,7 @@ import java.util.UUID
 import cats.Eq
 import cats.effect.Sync
 import cats.implicits._
+import cats.Order
 
 import io.circe.{Decoder, Encoder}
 import scodec.bits.ByteVector
@@ -66,4 +67,7 @@ object Ident {
   implicit val decodeIdent: Decoder[Ident] =
     Decoder.decodeString.emap(Ident.fromString)
 
+  implicit val order: Order[Ident] =
+    Order.by(_.id)
+
 }
diff --git a/modules/common/src/main/scala/docspell/common/MetaProposal.scala b/modules/common/src/main/scala/docspell/common/MetaProposal.scala
index 62a9355f..36f4be1c 100644
--- a/modules/common/src/main/scala/docspell/common/MetaProposal.scala
+++ b/modules/common/src/main/scala/docspell/common/MetaProposal.scala
@@ -2,9 +2,9 @@ package docspell.common
 
 import java.time.LocalDate
 
+import cats.Order
 import cats.data.NonEmptyList
 import cats.implicits._
-import cats.kernel.Order
 
 import docspell.common.MetaProposal.Candidate
 import docspell.common._
@@ -74,6 +74,9 @@ object MetaProposal {
     implicit val jsonDecoder: Decoder[Candidate] =
       deriveDecoder[Candidate]
 
+    implicit val order: Order[Candidate] =
+      Order.by(_.ref)
+
     /** This deviates from standard order to sort None at last.
       */
     val weightOrder: Order[Option[Double]] = new Order[Option[Double]] {
diff --git a/modules/common/src/main/scala/docspell/common/MetaProposalList.scala b/modules/common/src/main/scala/docspell/common/MetaProposalList.scala
index 04cedb30..33865484 100644
--- a/modules/common/src/main/scala/docspell/common/MetaProposalList.scala
+++ b/modules/common/src/main/scala/docspell/common/MetaProposalList.scala
@@ -52,7 +52,8 @@ case class MetaProposalList private (proposals: List[MetaProposal]) {
       (map, next) =>
         map.get(next.proposalType) match {
           case Some(MetaProposal(mt, values)) =>
-            val cand = NonEmptyList(values.head, next.values.toList ++ values.tail)
+            val cand =
+              NonEmptyList(values.head, next.values.toList ++ values.tail).distinct
             map.updated(next.proposalType, MetaProposal(mt, MetaProposal.flatten(cand)))
           case None =>
             map.updated(next.proposalType, next)
diff --git a/modules/common/src/test/scala/docspell/common/MetaProposalListTest.scala b/modules/common/src/test/scala/docspell/common/MetaProposalListTest.scala
index 44a6cfc2..c35bafcc 100644
--- a/modules/common/src/test/scala/docspell/common/MetaProposalListTest.scala
+++ b/modules/common/src/test/scala/docspell/common/MetaProposalListTest.scala
@@ -99,4 +99,34 @@ object MetaProposalListTest extends SimpleTestSuite {
       )
     )
   }
+
+  test("insert second, remove duplicates") {
+    val cand1 = Candidate(IdRef(Ident.unsafe("123"), "name"), Set.empty)
+    val cand2 = Candidate(IdRef(Ident.unsafe("456"), "name"), Set.empty)
+    val cand3 = Candidate(IdRef(Ident.unsafe("789"), "name"), Set.empty)
+    val cand5 = Candidate(IdRef(Ident.unsafe("def"), "name"), Set.empty)
+
+    val mpl1 = MetaProposalList
+      .of(
+        MetaProposal(MetaProposalType.CorrOrg, NonEmptyList.of(cand1, cand2)),
+        MetaProposal(MetaProposalType.ConcPerson, NonEmptyList.of(cand3))
+      )
+
+    val mpl2 = MetaProposalList
+      .of(
+        MetaProposal(MetaProposalType.CorrOrg, NonEmptyList.of(cand1)),
+        MetaProposal(MetaProposalType.ConcPerson, NonEmptyList.of(cand5))
+      )
+
+    val result = mpl1.insertSecond(mpl2)
+    assertEquals(
+      result,
+      MetaProposalList(
+        List(
+          MetaProposal(MetaProposalType.CorrOrg, NonEmptyList.of(cand1, cand2)),
+          MetaProposal(MetaProposalType.ConcPerson, NonEmptyList.of(cand3, cand5))
+        )
+      )
+    )
+  }
 }