diff --git a/tool/src/org/antlr/v4/analysis/LinearApproximator.java b/tool/src/org/antlr/v4/analysis/LinearApproximator.java
index e75a79166..6ef7ca3f6 100644
--- a/tool/src/org/antlr/v4/analysis/LinearApproximator.java
+++ b/tool/src/org/antlr/v4/analysis/LinearApproximator.java
@@ -25,7 +25,7 @@ public class LinearApproximator {
 
 	int max_k = MAX_LINEAR_APPROXIMATE_DEPTH;
 
-	/** Records state of a LOOK operation */
+	/** Records state of a LOOK operation; used just for lookahead busy checks */
 	static class LookaheadNFAConfig {
 		public NFAState s;
 		public int k;