diff --git a/gradle/generation/javacc.gradle b/gradle/generation/javacc.gradle
index fc51dae6ec6..b639d01a37c 100644
--- a/gradle/generation/javacc.gradle
+++ b/gradle/generation/javacc.gradle
@@ -269,6 +269,8 @@ class JavaCCTask extends DefaultTask {
    * Apply closures to all generated files before they're copied back
    * to mainline code.
    */
+  // A subtle bug here is that this makes it not an input... should be a list of replacements instead?
+  @Internal
   List<Closure<FileTree>> afterGenerate = new ArrayList<>()
 
   @OutputFiles
diff --git a/gradle/generation/jflex.gradle b/gradle/generation/jflex.gradle
index aa60d7fa9e2..02e8da940cb 100644
--- a/gradle/generation/jflex.gradle
+++ b/gradle/generation/jflex.gradle
@@ -222,7 +222,7 @@ class JFlexTask extends DefaultTask {
   @InputFile
   File skeleton
 
-  @Optional
+  @Internal
   String heapSize
 
   @OutputFile