diff --git a/third_party/com/github/bazelbuild/bazel/src/main/protobuf/crosstool_config.proto b/third_party/com/github/bazelbuild/bazel/src/main/protobuf/crosstool_config.proto
index 98d4fe3..361710d 100644
--- a/third_party/com/github/bazelbuild/bazel/src/main/protobuf/crosstool_config.proto
+++ b/third_party/com/github/bazelbuild/bazel/src/main/protobuf/crosstool_config.proto
@@ -16,11 +16,11 @@
 
 syntax = "proto2";
 
-package com.google.devtools.build.lib.view.config.crosstool;
-
 
 option java_package = "com.google.devtools.build.lib.view.config.crosstool";
 
+package com.google.devtools.build.lib.view.config.crosstool;
+
 // A description of a toolchain, which includes all the tools generally expected
 // to be available for building C/C++ targets, based on the GNU C compiler.
 //
@@ -148,7 +148,17 @@ message CToolchain {
     // unconditionally for every action specified.
     repeated WithFeatureSet with_feature = 3;
 
-    // Legacy field, ignored by Bazel.
+    // Deprecated (https://github.com/bazelbuild/bazel/issues/7008) - use
+    // expand_if_all_available in flag_group
+    //
+    // A list of build variables that this feature set needs, but which are
+    // allowed to not be set. If any of the build variables listed is not
+    // set, the feature set will not be expanded.
+    //
+    // NOTE: Consider alternatives before using this; usually tools should
+    // consistently create the same set of files, even if empty; use this
+    // only for backwards compatibility with already existing behavior in tools
+    // that are currently not worth changing.
     repeated string expand_if_all_available = 4;
   }