diff --git a/src/main/java/com/google/devtools/build/lib/analysis/config/BuildOptions.java b/src/main/java/com/google/devtools/build/lib/analysis/config/BuildOptions.java
index a8ac70f..ba4e6ac 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/config/BuildOptions.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/config/BuildOptions.java
@@ -901,6 +901,8 @@
      */
     public static ConfigurationComparer.Result compareFragments(
         OptionsDiffForReconstruction left, OptionsDiffForReconstruction right) {
+      // TODO: Add support for marking Starlark options as known default when trimming
+      // (sentinel object?)
       Preconditions.checkArgument(
           Arrays.equals(left.baseFingerprint, right.baseFingerprint),
           "Can't compare diffs with different bases: %s and %s",