diff --git a/src/core/operations/Arithmetic.js b/src/core/operations/Arithmetic.js
index ffcb6c86..1151c28f 100644
--- a/src/core/operations/Arithmetic.js
+++ b/src/core/operations/Arithmetic.js
@@ -57,7 +57,7 @@ const Arithmetic = {
         if (num === null) {
             return "";
         }
-        return num;
+        return num.toString();
     },