diff --git a/src/main/java/com/google/devtools/build/skyframe/BuildingState.java b/src/main/java/com/google/devtools/build/skyframe/BuildingState.java
index c410a41..cbedfd1 100644
--- a/src/main/java/com/google/devtools/build/skyframe/BuildingState.java
+++ b/src/main/java/com/google/devtools/build/skyframe/BuildingState.java
@@ -38,9 +38,11 @@
  * classes should instantiate a {@code BuildingState} object or call any of its methods directly.
  * It is in a separate file solely to keep the {@link NodeEntry} class readable. In particular, the
  * caller must synchronize access to this class.
+ *
+ * <p>This class is not intended to be used outside of Skyframe.
  */
 @ThreadCompatible
-final class BuildingState implements Serializable {
+public final class BuildingState implements Serializable {
   /**
    * During its life, a node can go through states as follows:
    * <ol>