diff --git a/src/dotty/tools/backend/jvm/CollectSuperCalls.scala b/src/dotty/tools/backend/jvm/CollectSuperCalls.scala
index 8f9b067ba7ac..e504047f3fb9 100644
--- a/src/dotty/tools/backend/jvm/CollectSuperCalls.scala
+++ b/src/dotty/tools/backend/jvm/CollectSuperCalls.scala
@@ -20,8 +20,11 @@ class CollectSuperCalls extends MiniPhaseTransform {
 
   override def transformSelect(tree: Select)(implicit ctx: Context, info: TransformerInfo): Tree = {
     tree.qualifier match {
-      case Super(qual: This, mix) if mix.nonEmpty =>
-        val classSymbol = qual.symbol.asClass.classSymbol
+      case Super(qual, mix) if mix.nonEmpty =>
+        val classSymbol: ClassSymbol = qual match {
+          case qual: This => qual.symbol.asClass.classSymbol
+          case qual => qual.symbol.info.classSymbol.asClass
+        }
         registerSuperCall(classSymbol, tree.symbol.owner.asClass)
       case _ =>
     }
diff --git a/src/dotty/tools/backend/jvm/DottyBackendInterface.scala b/src/dotty/tools/backend/jvm/DottyBackendInterface.scala
index 30934605bd21..34bcd0757cef 100644
--- a/src/dotty/tools/backend/jvm/DottyBackendInterface.scala
+++ b/src/dotty/tools/backend/jvm/DottyBackendInterface.scala
@@ -747,9 +747,13 @@ class DottyBackendInterface(outputDirectory: AbstractFile, val superCallsMap: Ma
      */
     def superInterfaces: List[Symbol] = {
       val directlyInheritedTraits = decorateSymbol(sym).directlyInheritedTraits
+      val directlyInheritedTraitsSet = directlyInheritedTraits.toSet
       val allBaseClasses = directlyInheritedTraits.iterator.flatMap(_.symbol.asClass.baseClasses.drop(1)).toSet
       val superCalls = superCallsMap.getOrElse(sym, Set.empty)
-      directlyInheritedTraits.filter(t => !allBaseClasses(t) || superCalls(t))
+      val additional = (superCalls -- directlyInheritedTraitsSet).filter(_.is(Flags.Trait))
+//      if (additional.nonEmpty)
+//        println(s"$fullName: adding supertraits $additional")
+      directlyInheritedTraits.filter(t => !allBaseClasses(t) || superCalls(t)) ++ additional
     }
 
     /**