diff --git a/third_party/bazel/src/main/protobuf/crosstool_config.proto b/third_party/bazel/src/main/protobuf/crosstool_config.proto
index 7f9430605d6..45ad1e599fb 100644
--- a/third_party/bazel/src/main/protobuf/crosstool_config.proto
+++ b/third_party/bazel/src/main/protobuf/crosstool_config.proto
@@ -114,6 +114,7 @@ message CToolchain {
   message EnvEntry {
     required string key = 1;
     required string value = 2;
+    repeated string expand_if_all_available = 3;
   }
 
   // A set of features; used to support logical 'and' when specifying feature