diff --git a/build.gradle b/build.gradle
index 45e8cab52ad..bfd1b8b4725 100644
--- a/build.gradle
+++ b/build.gradle
@@ -799,6 +799,9 @@ subprojects {
     createCheckTypeTask(project.name, 'Signature',
         'org.checkerframework.checker.signature.SignatureChecker')
 
+    // The checkNullness task runs on all code, but it only *checks* the following code:
+    //  * All files outside the 'framework' and 'checker' subprojects.
+    //  * In the 'framework' and 'checker' subprojects, files with `@AnnotatedFor("nullness")`.
     if (project.name.is('framework') || project.name.is('checker')) {
       createCheckTypeTask(project.name, 'Nullness',
           'org.checkerframework.checker.nullness.NullnessChecker',