diff --git a/compiler/src/dotty/tools/dotc/typer/Namer.scala b/compiler/src/dotty/tools/dotc/typer/Namer.scala
index e770d2c615f3..867fd1d0ebae 100644
--- a/compiler/src/dotty/tools/dotc/typer/Namer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Namer.scala
@@ -590,8 +590,10 @@ class Namer { typer: Typer =>
     def createLinks(classTree: TypeDef, moduleTree: TypeDef)(implicit ctx: Context) = {
       val claz = ctx.effectiveScope.lookup(classTree.name)
       val modl = ctx.effectiveScope.lookup(moduleTree.name)
-      ctx.synthesizeCompanionMethod(nme.COMPANION_CLASS_METHOD, claz, modl).entered
-      ctx.synthesizeCompanionMethod(nme.COMPANION_MODULE_METHOD, modl, claz).entered
+      if (claz.isClass && modl.isClass) {
+        ctx.synthesizeCompanionMethod(nme.COMPANION_CLASS_METHOD, claz, modl).entered
+        ctx.synthesizeCompanionMethod(nme.COMPANION_MODULE_METHOD, modl, claz).entered
+      }
     }
 
     def createCompanionLinks(implicit ctx: Context): Unit = {
diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index 5c722a1c92c6..5f023820bc07 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -1141,20 +1141,19 @@ class Typer extends Namer
         bindings1, expansion1)
   }
 
-  def typedTypeTree(tree: untpd.TypeTree, pt: Type)(implicit ctx: Context): TypeTree = track("typedTypeTree") {
+  def typedTypeTree(tree: untpd.TypeTree, pt: Type)(implicit ctx: Context): Tree = track("typedTypeTree") {
     tree match {
       case tree: untpd.DerivedTypeTree =>
         tree.ensureCompletions
-        try
-          TypeTree(tree.derivedType(tree.attachment(untpd.OriginalSymbol))) withPos tree.pos
-        // btw, no need to remove the attachment. The typed
-        // tree is different from the untyped one, so the
-        // untyped tree is no longer accessed after all
-        // accesses with typedTypeTree are done.
-        catch {
-          case ex: NoSuchElementException =>
-            println(s"missing OriginalSymbol for ${ctx.owner.ownersIterator.toList}")
-            throw ex
+        tree.getAttachment(untpd.OriginalSymbol) match {
+          case Some(origSym) =>
+            TypeTree(tree.derivedType(origSym)).withPos(tree.pos)
+            // btw, no need to remove the attachment. The typed
+            // tree is different from the untyped one, so the
+            // untyped tree is no longer accessed after all
+            // accesses with typedTypeTree are done.
+          case None =>
+            errorTree(tree, "Something's wrong: missing original symbol for type tree")
         }
       case _ =>
         tree.withType(
diff --git a/tests/neg/i1771.scala b/tests/neg/i1771.scala
new file mode 100644
index 000000000000..6b96ba3af044
--- /dev/null
+++ b/tests/neg/i1771.scala
@@ -0,0 +1,4 @@
+class GBTree[B] {
+  class Tree[A, B]; class Node[A, B](value: Node[A, B]) extends Tree[A, B]
+  case class B[A, B]() extends Tree[A, B]  // error: double definition
+}