diff --git a/lib/utils/util.js b/lib/utils/util.js
index 248e6e42..18fa796f 100644
--- a/lib/utils/util.js
+++ b/lib/utils/util.js
@@ -392,6 +392,11 @@ util.isHex256 = function isHex256(hash) {
 
 /**
  * Test whether a string qualifies as a float.
+ *
+ * This is stricter than checking if the result of parseFloat() is NaN
+ * as, e.g. parseFloat successfully parses the string '1.2.3' as 1.2, and
+ * we also check that the value is a string.
+ *
  * @param {String?} value
  * @returns {Boolean}
  */