diff --git a/src/core/Utils.mjs b/src/core/Utils.mjs
index a9c381d7..707720cc 100755
--- a/src/core/Utils.mjs
+++ b/src/core/Utils.mjs
@@ -1275,7 +1275,7 @@ class Utils {
     static modInv(x, y) {
         x %= y;
         for (let i = 1; i < y; i++) {
-            if ((x * i) % 26 === 1) {
+            if ((x * i) % y === 1) {
                 return i;
             }
         }