diff --git a/test/validator/samples/general-siblings-combinator-in-custom-element-selects-slot-fallback/_config.js b/test/validator/samples/general-siblings-combinator-in-custom-element-selects-slot-fallback/_config.js
new file mode 100644
index 0000000000..6fc797bfd8
--- /dev/null
+++ b/test/validator/samples/general-siblings-combinator-in-custom-element-selects-slot-fallback/_config.js
@@ -0,0 +1,3 @@
+export default {
+	customElement: true
+};
diff --git a/test/validator/samples/general-siblings-combinator-in-custom-element-selects-slot-fallback/input.svelte b/test/validator/samples/general-siblings-combinator-in-custom-element-selects-slot-fallback/input.svelte
new file mode 100644
index 0000000000..ffaeb2c097
--- /dev/null
+++ b/test/validator/samples/general-siblings-combinator-in-custom-element-selects-slot-fallback/input.svelte
@@ -0,0 +1,20 @@
+<svelte:options tag="my-element" />
+
+<h1>Heading 1</h1>
+<span>Span 1</span>
+<span>Span 2</span>
+<slot>
+	<p>Paragraph 2</p>
+</slot>
+
+<style>
+	/* This will not get picked up */
+	h1 ~ p {
+		color: red;
+	}
+
+	/* This will be picked up */
+	h1 ~ slot > p {
+		color: red;
+	}
+</style>
diff --git a/test/validator/samples/general-siblings-combinator-in-custom-element-selects-slot-fallback/warnings.json b/test/validator/samples/general-siblings-combinator-in-custom-element-selects-slot-fallback/warnings.json
new file mode 100644
index 0000000000..0336660caf
--- /dev/null
+++ b/test/validator/samples/general-siblings-combinator-in-custom-element-selects-slot-fallback/warnings.json
@@ -0,0 +1,14 @@
+[
+  {
+    "code": "css-unused-selector",
+    "message": "Unused CSS selector \"h1 ~ p\"",
+    "start": {
+      "column": 1,
+      "line": 12
+    },
+    "end": {
+      "column": 7,
+      "line": 12
+    }
+  }
+]
\ No newline at end of file
diff --git a/test/validator/samples/siblings-combinator-in-custom-element-selects-slot-fallback/_config.js b/test/validator/samples/siblings-combinator-in-custom-element-selects-slot-fallback/_config.js
new file mode 100644
index 0000000000..6fc797bfd8
--- /dev/null
+++ b/test/validator/samples/siblings-combinator-in-custom-element-selects-slot-fallback/_config.js
@@ -0,0 +1,3 @@
+export default {
+	customElement: true
+};
diff --git a/test/validator/samples/siblings-combinator-in-custom-element-selects-slot-fallback/input.svelte b/test/validator/samples/siblings-combinator-in-custom-element-selects-slot-fallback/input.svelte
new file mode 100644
index 0000000000..1d98415321
--- /dev/null
+++ b/test/validator/samples/siblings-combinator-in-custom-element-selects-slot-fallback/input.svelte
@@ -0,0 +1,18 @@
+<svelte:options tag="custom-element" />
+
+<h1>test</h1>
+<slot>
+  <span>Hello</span>
+</slot>
+
+<style>
+	/* This will not be picked up */
+  h1 + span {
+    color: red;
+  }
+
+	/* This will be picked up */
+	h1 + slot > span {
+		color: red;
+	}
+</style>
diff --git a/test/validator/samples/siblings-combinator-in-custom-element-selects-slot-fallback/warnings.json b/test/validator/samples/siblings-combinator-in-custom-element-selects-slot-fallback/warnings.json
new file mode 100644
index 0000000000..3ef66ebf60
--- /dev/null
+++ b/test/validator/samples/siblings-combinator-in-custom-element-selects-slot-fallback/warnings.json
@@ -0,0 +1,14 @@
+[
+  {
+    "code": "css-unused-selector",
+    "end": {
+      "column": 11,
+      "line": 10
+    },
+    "message": "Unused CSS selector \"h1 + span\"",
+    "start": {
+      "column": 2,
+      "line": 10
+    }
+  }
+]
\ No newline at end of file