diff --git a/core/src/main/java/io/grpc/NameResolverProvider.java b/core/src/main/java/io/grpc/NameResolverProvider.java
index 601537438f..333632fe6c 100644
--- a/core/src/main/java/io/grpc/NameResolverProvider.java
+++ b/core/src/main/java/io/grpc/NameResolverProvider.java
@@ -30,14 +30,8 @@ import java.util.List;
  * exceptions may reasonably occur for implementation-specific reasons, implementations should
  * generally handle the exception gracefully and return {@code false} from {@link #isAvailable()}.
  */
-@ExperimentalApi
+@ExperimentalApi("https://github.com/grpc/grpc-java/issues/4159")
 public abstract class NameResolverProvider extends NameResolver.Factory {
-  /**
-   * The port number used in case the target or the underlying naming system doesn't provide a
-   * port number.
-   */
-  public static final Attributes.Key<Integer> PARAMS_DEFAULT_PORT =
-      NameResolver.Factory.PARAMS_DEFAULT_PORT;
   @VisibleForTesting
   static final Iterable<Class<?>> HARDCODED_CLASSES = new HardcodedClasses();