diff --git a/rules/require-array-join-separator.js b/rules/require-array-join-separator.js
index 50fa5c176a..b09b2f18eb 100644
--- a/rules/require-array-join-separator.js
+++ b/rules/require-array-join-separator.js
@@ -9,7 +9,11 @@ const messages = {
 
 const selector = matches([
 	// `foo.join()`
-	methodCallSelector({method: 'join', argumentsLength: 0}),
+	methodCallSelector({
+		method: 'join',
+		argumentsLength: 0,
+		includeOptionalMember: true,
+	}),
 	// `[].join.call(foo)` and `Array.prototype.join.call(foo)`
 	[
 		methodCallSelector({method: 'call', argumentsLength: 1}),
diff --git a/test/require-array-join-separator.mjs b/test/require-array-join-separator.mjs
index fa7740cb36..b0f861aa0e 100644
--- a/test/require-array-join-separator.mjs
+++ b/test/require-array-join-separator.mjs
@@ -8,7 +8,8 @@ test.snapshot({
 		'foo.join(",")',
 		'join()',
 		'foo.join(...[])',
-		'foo?.join()',
+		'foo.join?.()',
+		'foo?.join?.()',
 		'foo[join]()',
 		'foo["join"]()',
 		'[].join.call(foo, ",")',
@@ -71,5 +72,6 @@ test.snapshot({
 					)/**/
 			)
 		`,
+		'foo?.join()',
 	],
 });
diff --git a/test/snapshots/require-array-join-separator.mjs.md b/test/snapshots/require-array-join-separator.mjs.md
index 3a1d224163..820c0351f9 100644
--- a/test/snapshots/require-array-join-separator.mjs.md
+++ b/test/snapshots/require-array-join-separator.mjs.md
@@ -192,3 +192,19 @@ Generated by [AVA](https://avajs.dev).
          | ^^^^ Missing the separator argument.␊
       26 | )␊
     `
+
+## Invalid #8
+      1 | foo?.join()
+
+> Output
+
+    `␊
+      1 | foo?.join(',')␊
+    `
+
+> Error 1/1
+
+    `␊
+    > 1 | foo?.join()␊
+        |          ^^ Missing the separator argument.␊
+    `
diff --git a/test/snapshots/require-array-join-separator.mjs.snap b/test/snapshots/require-array-join-separator.mjs.snap
index 93be20ae95..e41d3d4a82 100644
Binary files a/test/snapshots/require-array-join-separator.mjs.snap and b/test/snapshots/require-array-join-separator.mjs.snap differ