diff --git a/runtime/src/main/java/org/capnproto/Capability.java b/runtime/src/main/java/org/capnproto/Capability.java
index 7b85d26..ebe8916 100644
--- a/runtime/src/main/java/org/capnproto/Capability.java
+++ b/runtime/src/main/java/org/capnproto/Capability.java
@@ -6,11 +6,11 @@ import java.util.concurrent.CompletionStage;
 
 public final class Capability {
 
-    public static abstract class BuilderContext {
+    static class BuilderContext {
         CapTableBuilder capTable;
     }
 
-    public static class ReaderContext {
+    static class ReaderContext {
         CapTableReader capTable;
     }