diff --git a/src/functions/functions.js b/src/functions/functions.js
index 9d9438c..568c16e 100644
--- a/src/functions/functions.js
+++ b/src/functions/functions.js
@@ -146,6 +146,7 @@ function cotAnswer(completion, separator) {
 
 function toEntityProperty(value) {
   if (value === null) {
+    // There is no concept of null in Excel's data model.
     return '';
   } else if (typeof value !== 'object') {
     return value;