diff --git a/source-driver.js b/source-driver.js
index cbc45443b2916d5969d87c90b4a2ad48d6e25491..a2b44801e62c1fac7bbf0b342fa3be9d0e3e83e2 100644
--- a/source-driver.js
+++ b/source-driver.js
@@ -1,7 +1,7 @@
 var source_file = 'var x = 2;\n';
 
 var tracer_files = [
-    // the tracer files
+    // the tracer files {file : , contents : with quotes and return escaped}
 ];
 
 // stdlib