1 files changed, 3 insertions, 2 deletions
diff --git a/src/main/scala/firrtl/transforms/BlackBoxSourceHelper.scala b/src/main/scala/firrtl/transforms/BlackBoxSourceHelper.scala
index 322634dd..d8d4a12b 100644
--- a/src/main/scala/firrtl/transforms/BlackBoxSourceHelper.scala
+++ b/src/main/scala/firrtl/transforms/BlackBoxSourceHelper.scala
@@ -6,7 +6,6 @@ import java.io.{File, FileNotFoundException, FileInputStream, FileOutputStream,
 
 import firrtl._
 import firrtl.annotations._
-import firrtl.options.PreservesAll
 
 import scala.collection.immutable.ListSet
 
@@ -55,7 +54,7 @@ class BlackBoxNotFoundException(fileName: String, message: String) extends Firrt
   * will set the directory where the Verilog will be written.  This annotation is typically be
   * set by the execution harness, or directly in the tests
   */
-class BlackBoxSourceHelper extends Transform with DependencyAPIMigration with PreservesAll[Transform] {
+class BlackBoxSourceHelper extends Transform with DependencyAPIMigration {
   import BlackBoxSourceHelper._
   private val DefaultTargetDir = new File(".")
 
@@ -65,6 +64,8 @@ class BlackBoxSourceHelper extends Transform with DependencyAPIMigration with Pr
 
   override def optionalPrerequisiteOf = Seq.empty
 
+  override def invalidates(a: Transform) = false
+
   /** Collect BlackBoxHelperAnnos and and find the target dir if specified
     * @param annos a list of generic annotations for this transform
     * @return BlackBoxHelperAnnos and target directory