diff --git a/packages/@markuplint/rules/src/permitted-contents/index.spec.ts b/packages/@markuplint/rules/src/permitted-contents/index.spec.ts
index 1bbac9bd4..2f48c2e7d 100644
--- a/packages/@markuplint/rules/src/permitted-contents/index.spec.ts
+++ b/packages/@markuplint/rules/src/permitted-contents/index.spec.ts
@@ -1501,4 +1501,29 @@ describe('Issues', () => {
 		const sourceCode = '<svg><text><tspan>Text</tspan></text></svg>';
 		expect((await mlRuleTest(rule, sourceCode)).violations).toStrictEqual([]);
 	});
+
+	test('#1451', async () => {
+		const astro = { parser: { '.*': '@markuplint/astro-parser' } };
+		const jsx = { parser: { '.*': '@markuplint/jsx-parser' } };
+		const pug = { parser: { '.*': '@markuplint/pug-parser' } };
+		const svelte = { parser: { '.*': '@markuplint/svelte-parser' } };
+		const vue = { parser: { '.*': '@markuplint/vue-parser' } };
+
+		expect((await mlRuleTest(rule, '<span><div></div></span>')).violations.length).toBe(1);
+		expect((await mlRuleTest(rule, '<span><Div></Div></span>')).violations.length).toBe(1);
+		expect((await mlRuleTest(rule, '<span><div></div></span>', astro)).violations.length).toBe(1);
+		expect((await mlRuleTest(rule, '<span><Div></Div></span>', astro)).violations.length).toBe(0);
+		expect((await mlRuleTest(rule, '<span><div></div></span>', jsx)).violations.length).toBe(1);
+		expect((await mlRuleTest(rule, '<span><Div></Div></span>', jsx)).violations.length).toBe(0);
+		expect((await mlRuleTest(rule, 'span: div', pug)).violations.length).toBe(1);
+		expect((await mlRuleTest(rule, 'span: Div', pug)).violations.length).toBe(1);
+		expect((await mlRuleTest(rule, '<span><div></div></span>', svelte)).violations.length).toBe(1);
+		expect((await mlRuleTest(rule, '<span><Div></Div></span>', svelte)).violations.length).toBe(0);
+		expect((await mlRuleTest(rule, '<template><span><div></div></span></template>', vue)).violations.length).toBe(
+			1,
+		);
+		expect((await mlRuleTest(rule, '<template><span><Div></Div></span></template>', vue)).violations.length).toBe(
+			0,
+		);
+	});
 });