diff --git a/src/main/java/com/google/devtools/build/lib/query2/RBuildFilesVisitor.java b/src/main/java/com/google/devtools/build/lib/query2/RBuildFilesVisitor.java
index 8e4a7b7..ed5dcd5 100644
--- a/src/main/java/com/google/devtools/build/lib/query2/RBuildFilesVisitor.java
+++ b/src/main/java/com/google/devtools/build/lib/query2/RBuildFilesVisitor.java
@@ -89,7 +89,10 @@
         if (resultUniquifier.unique(rdep)) {
           keysToUseForResult.add((PackageIdentifier) rdep.argument());
         }
-        // Every package has a dep on the external package, so we need to include those edges too.
+        // PackageValue(//p) has a transitive dep on the PackageValue(//external), so we need to
+        // make sure these dep paths are traversed. These dep paths go through the singleton
+        // WorkspaceNameValue(), and that node has a direct dep on PackageValue(//external), so it
+        // suffices to ensure we visit PackageValue(//external).
         if (rdep.equals(EXTERNAL_PACKAGE_KEY)) {
           keysToVisitNext.add(rdep);
         }