diff --git a/oauth2_http/java/com/google/auth/oauth2/OAuth2Credentials.java b/oauth2_http/java/com/google/auth/oauth2/OAuth2Credentials.java
index 682e255b8..94ddeb549 100644
--- a/oauth2_http/java/com/google/auth/oauth2/OAuth2Credentials.java
+++ b/oauth2_http/java/com/google/auth/oauth2/OAuth2Credentials.java
@@ -639,8 +639,8 @@ public void run() {
   public static class Builder {
 
     private AccessToken accessToken;
-    protected Duration refreshMargin = DEFAULT_REFRESH_MARGIN;
-    protected Duration expirationMargin = DEFAULT_EXPIRATION_MARGIN;
+    private Duration refreshMargin = DEFAULT_REFRESH_MARGIN;
+    private Duration expirationMargin = DEFAULT_EXPIRATION_MARGIN;
 
     protected Builder() {}