diff --git a/main/src/main/scala/sbt/internal/IncrementalTest.scala b/main/src/main/scala/sbt/internal/IncrementalTest.scala
index 0a9faaa7b..81462fab0 100644
--- a/main/src/main/scala/sbt/internal/IncrementalTest.scala
+++ b/main/src/main/scala/sbt/internal/IncrementalTest.scala
@@ -190,14 +190,20 @@ class ClassStamper private[sbt] (
       extraHashes: Seq[Digest],
       log: Logger,
   ): Option[Digest] =
-    val builder = Set.newBuilder[Digest]
-    analyses.foreach: analysis =>
-      internalStamp(builder, javaClassName, analysis, mutable.Set.empty, log)
-    val digests = builder.result().toSeq.sorted
-    // log.debug(s"test: transitiveStamp($javaClassName, $extraHashes) = $digests")
-    if digests.nonEmpty then Some(Digest.sha256Hash(digests ++ extraHashes*))
+    val digests = transitiveStamps(javaClassName, extraHashes, log)
+    if digests.nonEmpty then Some(Digest.sha256Hash(digests*))
     else None
 
+  private def transitiveStamps(
+      javaClassName: String,
+      extraHashes: Seq[Digest],
+      log: Logger,
+  ): Seq[Digest] =
+    val builder = Set.newBuilder[Digest]
+    analyses.foreach(internalStamp(builder, javaClassName, _, mutable.Set.empty, log))
+    val digests = builder.result().toSeq.sorted
+    digests ++ extraHashes
+
   private def internalStamp(
       builder: mutable.Builder[Digest, Set[Digest]],
       javaClassName: String,
@@ -221,7 +227,7 @@ class ClassStamper private[sbt] (
       relations
         .externalDeps(className)
         .foreach: libClassName =>
-          newBuilder ++= transitiveStamp(libClassName, Nil, log)
+          newBuilder ++= transitiveStamps(libClassName, Nil, log)
       relations
         .externalDeps(className)
         .foreach: libClassName =>