diff --git a/src/typed-function.mjs b/src/typed-function.mjs
index 55499f7..31c910e 100644
--- a/src/typed-function.mjs
+++ b/src/typed-function.mjs
@@ -1878,7 +1878,7 @@ function create () {
 
     if (existing) {
       if (options && options.override) {
-        to.conversionsTo.splice(existing.index, 1)
+        typed.removeConversion({ from: existing.from, to: conversion.to, convert: existing.convert })
       } else {
         throw new Error(
           'There is already a conversion from "' + conversion.from + '" to "' +
diff --git a/test/conversion.test.js b/test/conversion.test.js
index 690e6c0..5da72d3 100644
--- a/test/conversion.test.js
+++ b/test/conversion.test.js
@@ -101,6 +101,11 @@ describe('conversion', function () {
   it('should override a conversion using addConversions', function () {
     const typed2 = typed.create()
 
+    // we add an unrelated conversion to ensure we cannot misuse the internal .index 
+    // (which is more like an auto incrementing id)
+    const conversionUnrelated = { from: 'string', to: 'boolean', convert: () => 'c' }
+    typed2.addConversion(conversionUnrelated)
+
     const conversionA = { from: 'number', to: 'string', convert: () => 'a' }
     const conversionB = { from: 'number', to: 'string', convert: () => 'b' }