diff --git a/lib/rules/custom-event-name-casing.js b/lib/rules/custom-event-name-casing.js
index 5c33980ec..c3d74c17d 100644
--- a/lib/rules/custom-event-name-casing.js
+++ b/lib/rules/custom-event-name-casing.js
@@ -85,11 +85,6 @@ module.exports = {
             },
             OBJECT_OPTION_SCHEMA
           ]
-        },
-        // For backward compatibility
-        {
-          type: 'array',
-          items: [OBJECT_OPTION_SCHEMA]
         }
       ]
     },
@@ -102,13 +97,8 @@ module.exports = {
     /** @type {Map<ObjectExpression|Program, {contextReferenceIds:Set<Identifier>,emitReferenceIds:Set<Identifier>}>} */
     const setupContexts = new Map()
     let emitParamName = ''
-    const options =
-      context.options.length === 1 && typeof context.options[0] !== 'string'
-        ? // For backward compatibility
-          [undefined, context.options[0]]
-        : context.options
-    const caseType = options[0] || DEFAULT_CASE
-    const objectOption = options[1] || {}
+    const caseType = context.options[0] || DEFAULT_CASE
+    const objectOption = context.options[1] || {}
     const caseChecker = casing.getChecker(caseType)
     /** @type {RegExp[]} */
     const ignores = (objectOption.ignores || []).map(toRegExp)
diff --git a/tests/lib/rules/custom-event-name-casing.js b/tests/lib/rules/custom-event-name-casing.js
index 6b6e84c80..7c7b87cda 100644
--- a/tests/lib/rules/custom-event-name-casing.js
+++ b/tests/lib/rules/custom-event-name-casing.js
@@ -237,18 +237,6 @@ tester.run('custom-event-name-casing', rule, {
       ]
     },
 
-    // For backward compatibility
-    {
-      filename: 'test.vue',
-      code: `
-      <template>
-        <input
-          @click="$emit('fooBar')">
-      </template>
-      `,
-      options: [{ ignores: ['fooBar'] }]
-    },
-
     // camelCase
     {
       filename: 'test.vue',