diff --git a/src/util/cast.js b/src/util/cast.js
index a8a1535b8..79e76b134 100644
--- a/src/util/cast.js
+++ b/src/util/cast.js
@@ -90,6 +90,15 @@ Cast.toRgbColorObject = function (value) {
     return color;
 };
 
+/**
+ * Determine if a Scratch argument is a white space string (or null / empty).
+ * @param {*} val value to check.
+ * @return {boolean} True if the argument is all white spaces or null / empty.
+ */
+Cast.isWhiteSpace = function (val) {
+    return val === null || typeof val === 'string' && val.trim().length === 0;
+};
+
 /**
  * Compare two values, using Scratch cast, case-insensitive string compare, etc.
  * In Scratch 2.0, this is captured by `interp.compare.`
@@ -100,6 +109,11 @@ Cast.toRgbColorObject = function (value) {
 Cast.compare = function (v1, v2) {
     var n1 = Number(v1);
     var n2 = Number(v2);
+    if (n1 === 0 && Cast.isWhiteSpace(v1)) {
+        n1 = NaN;
+    } else if (n2 === 0 && Cast.isWhiteSpace(v2)) {
+        n2 = NaN;
+    }
     if (isNaN(n1) || isNaN(n2)) {
         // At least one argument can't be converted to a number.
         // Scratch compares strings as case insensitive.