diff --git a/core/src/main/scala/shapeless/sized.scala b/core/src/main/scala/shapeless/sized.scala
index 159384c29..3915d25c2 100644
--- a/core/src/main/scala/shapeless/sized.scala
+++ b/core/src/main/scala/shapeless/sized.scala
@@ -238,6 +238,9 @@ object AdditiveCollection extends AdditiveCollectionVersionSpecific {
 
   implicit def defaultAdditiveCollection[T]: AdditiveCollection[collection.immutable.IndexedSeq[T]] =
     instance.asInstanceOf[AdditiveCollection[collection.immutable.IndexedSeq[T]]]
+
+  implicit def seqAdditiveCollection[T]: AdditiveCollection[Seq[T]] =
+    instance.asInstanceOf[AdditiveCollection[Seq[T]]]
 }
 
 class DefaultToIndexedSeq[CC[_]]