diff --git a/compiler/src/dotty/tools/dotc/core/SymDenotations.scala b/compiler/src/dotty/tools/dotc/core/SymDenotations.scala
index bfaa12729090..15c943b29640 100644
--- a/compiler/src/dotty/tools/dotc/core/SymDenotations.scala
+++ b/compiler/src/dotty/tools/dotc/core/SymDenotations.scala
@@ -1056,7 +1056,10 @@ object SymDenotations {
       else overriddenFromType(owner.asClass.classInfo.selfType)
 
     private def overriddenFromType(tp: Type)(implicit ctx: Context): Iterator[Symbol] =
-      tp.baseClasses.tail.iterator map overriddenSymbol filter (_.exists)
+      tp.baseClasses match {
+        case _ :: inherited => inherited.iterator map overriddenSymbol filter (_.exists)
+        case Nil => Iterator.empty
+      }
 
     /** The symbol overriding this symbol in given subclass `ofclazz`.
      *
diff --git a/compiler/src/dotty/tools/dotc/interactive/InteractiveDriver.scala b/compiler/src/dotty/tools/dotc/interactive/InteractiveDriver.scala
index 8bfc6fef3eb3..a27db1d5d5db 100644
--- a/compiler/src/dotty/tools/dotc/interactive/InteractiveDriver.scala
+++ b/compiler/src/dotty/tools/dotc/interactive/InteractiveDriver.scala
@@ -179,6 +179,21 @@ class InteractiveDriver(settings: List[String]) extends Driver {
 
   private val compiler: Compiler = new InteractiveCompiler
 
+  /** Remove attachments and error out completers. The goal is to avoid
+   *  having a completer hanging in a typed tree which can capture the context
+   *  of a previous run. Note that typed trees can have untyped or partially
+   *  typed children if the source contains errors.
+   */
+  private def cleanup(tree: tpd.Tree)(implicit ctx: Context): Unit = tree.foreachSubTree { t =>
+    if (t.hasType) {
+      if (t.symbol.exists) {
+        if (!t.symbol.isCompleted) t.symbol.info = UnspecifiedErrorType
+        t.symbol.annotations.foreach(annot => cleanup(annot.tree))
+      }
+    }
+    t.removeAllAttachments()
+  }
+
   def run(uri: URI, sourceCode: String): List[MessageContainer] = {
     val previousCtx = myCtx
     try {
@@ -200,6 +215,7 @@ class InteractiveDriver(settings: List[String]) extends Driver {
       run.compileSources(List(source))
       run.printSummary()
       val t = run.units.head.tpdTree
+      cleanup(t)
       myOpenedTrees(uri) = topLevelClassTrees(t, source)
 
       reporter.removeBufferedMessages
diff --git a/compiler/src/dotty/tools/dotc/util/Attachment.scala b/compiler/src/dotty/tools/dotc/util/Attachment.scala
index 20facfd97544..ed71aba1c90b 100644
--- a/compiler/src/dotty/tools/dotc/util/Attachment.scala
+++ b/compiler/src/dotty/tools/dotc/util/Attachment.scala
@@ -92,5 +92,8 @@ object Attachment {
       assert(!getAttachment(key).isDefined, s"duplicate attachment for key $key")
       next = new Link(key, value, next)
     }
+
+    final def removeAllAttachments() =
+      next = null
   }
 }