diff --git a/README.md b/README.md
index 2c1907aec0..866e8f4071 100644
--- a/README.md
+++ b/README.md
@@ -197,6 +197,13 @@ Fetch the tags from the upstream:
 ```
 git fetch --tags upstream
 ```
+
+## Scoping which projects are included by `sbt`
+
+* when `STTP_NATIVE` is set, Scala native projects are included in the build (when running `sbt`)
+* when `ALSO_LOOM` is set, projects using virtual threads and requiring Java 21 are included in the build 
+* when `ONLY_LOOM` is set, only projects using virtual threads are included in the build
+
 ### Testing locally
 
 The JS tests use [Gecko instead of Chrome](https://github.com/scala-js/scala-js-env-selenium/issues/119), although this
diff --git a/build.sbt b/build.sbt
index a4773f8cee..63304354ca 100644
--- a/build.sbt
+++ b/build.sbt
@@ -263,6 +263,9 @@ lazy val allAggregates: Seq[ProjectReference] = {
   if (sys.env.isDefinedAt("ONLY_LOOM")) {
     println("[info] ONLY_LOOM defined, including only loom-based projects")
     filteredByNative.filter(p => (p.toString.contains("Loom") || p.toString.contains("nima")))
+  } else if (sys.env.isDefinedAt("ALSO_LOOM")) {
+    println("[info] ALSO_LOOM defined, including also loom-based projects")
+    filteredByNative
   } else {
     println("[info] ONLY_LOOM *not* defined, *not* including loom-based-projects")
     filteredByNative.filterNot(p => (p.toString.contains("Loom") || p.toString.contains("nima")))