diff --git a/packages/eslint-plugin/src/rules/key-spacing.ts b/packages/eslint-plugin/src/rules/key-spacing.ts
index 7bd325172983..fab4ced919ae 100644
--- a/packages/eslint-plugin/src/rules/key-spacing.ts
+++ b/packages/eslint-plugin/src/rules/key-spacing.ts
@@ -84,18 +84,9 @@ export default util.createRule<Options, MessageIds>({
     /**
      * To handle index signatures, be able to get the end position of the parameters
      */
-    function getKeyLocEnd(
-      node:
-        | TSESTree.TSIndexSignature
-        | TSESTree.TSPropertySignature
-        | TSESTree.PropertyDefinition,
-    ): TSESTree.Position {
-      if ('key' in node) {
-        return node.key.loc.end;
-      }
-
+    function getKeyLocEnd(node: KeyTypeNode): TSESTree.Position {
       return getLastTokenBeforeColon(
-        node.parameters[node.parameters.length - 1],
+        'key' in node ? node.key : node.parameters[node.parameters.length - 1],
       ).loc.end;
     }
 
diff --git a/packages/eslint-plugin/tests/rules/key-spacing.test.ts b/packages/eslint-plugin/tests/rules/key-spacing.test.ts
index 64e037b7336d..8911bce8d484 100644
--- a/packages/eslint-plugin/tests/rules/key-spacing.test.ts
+++ b/packages/eslint-plugin/tests/rules/key-spacing.test.ts
@@ -16,6 +16,10 @@ ruleTester.run('key-spacing', rule, {
       code: 'interface X {\n  a:   number;\n  abc: string\n};',
       options: [{ align: 'value' }],
     },
+    {
+      code: 'interface X {\n  a?:  number;\n  abc: string\n};',
+      options: [{ align: 'value' }],
+    },
     {
       code: 'interface X {\n  a:   number;\n  // Some comment\n  abc: string\n};',
       options: [{ align: 'value' }],
@@ -36,6 +40,10 @@ ruleTester.run('key-spacing', rule, {
       code: 'class X {\n  a:   number;\n  abc: string\n};',
       options: [{ align: 'value' }],
     },
+    {
+      code: 'class X {\n  a?:  number;\n  abc: string\n};',
+      options: [{ align: 'value' }],
+    },
     {
       code: 'class X {\n  a: number;\n\n  abc: string\n};',
       options: [{ align: 'value' }],