diff --git a/java/hiddenapi_modular.go b/java/hiddenapi_modular.go
index 8011f34..bf99757 100644
--- a/java/hiddenapi_modular.go
+++ b/java/hiddenapi_modular.go
@@ -947,6 +947,7 @@
 	HiddenAPIFlagOutput
 
 	// The map from base module name to the path to the encoded boot dex file.
+	// This field is not available in prebuilt apexes
 	EncodedBootDexFilesByModule bootDexJarByModule
 }