diff --git a/exercises/practice/forth/.meta/proof.ci.js b/exercises/practice/forth/.meta/proof.ci.js
index b46c5586c6..b26d7d111f 100644
--- a/exercises/practice/forth/.meta/proof.ci.js
+++ b/exercises/practice/forth/.meta/proof.ci.js
@@ -67,7 +67,7 @@ export class Forth {
 
   performCommand(command) {
     if (command.arity > this.stack.length) {
-      if (this.stack.length == 1) {
+      if (this.stack.length === 1) {
         throw new Error('Only one value on the stack');
       }
       throw new Error('Stack empty');