diff --git a/src/markdown/frontmatter.ts b/src/markdown/frontmatter.ts
index 0994a76875..44f497524b 100644
--- a/src/markdown/frontmatter.ts
+++ b/src/markdown/frontmatter.ts
@@ -34,7 +34,7 @@ function coerceFrontmatterValue(value: unknown): string | undefined {
 
 function parseYamlFrontmatter(block: string): ParsedFrontmatter | null {
   try {
-    const parsed = YAML.parse(block) as unknown;
+    const parsed = YAML.parse(block, { schema: "core" }) as unknown;
     if (!parsed || typeof parsed !== "object" || Array.isArray(parsed)) {
       return null;
     }