diff --git a/src/compiler/emitter.ts b/src/compiler/emitter.ts
index 4813e62b60e..504a384f579 100644
--- a/src/compiler/emitter.ts
+++ b/src/compiler/emitter.ts
@@ -3998,6 +3998,9 @@ module ts {
 
                 increaseIndent();
                 emitDetachedComments(body.statements);
+
+                // Emit all the directive prologues (like "use strict").  These have to come before
+                // any other preamble code we write (like parameter initializers).
                 var startIndex = emitDirectivePrologues(body.statements, /*startWithNewLine*/ true);
                 emitFunctionBodyPreamble(node);
                 decreaseIndent();