diff --git a/lib/sealed-join.ts b/lib/sealed-join.ts
index 24e8afeba..3c048ddf4 100644
--- a/lib/sealed-join.ts
+++ b/lib/sealed-join.ts
@@ -136,7 +136,7 @@ export function fileRecords(file: string, text: string): Field[][] | null {
 
 /** Joined-record fingerprints of one file's text; null when it cannot be checked. */
 export function fileJoins(file: string, text: string, p: JoinPolicy): Joins | null {
-  const folded = normalizeKey(text);
+  const folded = normalizeKey(text.replace(/"/g, ''));
   if (!text.includes('\\u') && !p.label_keys.some(k => folded.includes(normalizeKey(k)))) return new Map();
   const records = fileRecords(file, text);
   if (!records) return null;
diff --git a/test/sealed-join.test.ts b/test/sealed-join.test.ts
index f53ad620f..3b92ce1a8 100644
--- a/test/sealed-join.test.ts
+++ b/test/sealed-join.test.ts
@@ -88,6 +88,7 @@ describe('formats and matching', () => {
       'k.jsonl': `{"${HEAD_B}":{"stratum":"seeded"}}\n`,
       'l.json': '{"units":{"unit-one":{"stratum":"decoy"}}}\n',
       'm.tsv': '"Stratum"\t"head"\n"decoy"\t"5b7db3a"\n',
+      'n.csv': '"Strat"um,head\ndecoy,5b7db3a\n',
       'tsconfig.json': '{\n  // a comment, so not strict JSON\n  "compilerOptions": { "strict": true }\n}\n',
     });
     expect(found(s).sort((a, b) => a.file.localeCompare(b.file))).toEqual([
@@ -99,6 +100,7 @@ describe('formats and matching', () => {
       { rule: 'sealed.label_join', file: 'j.json', commit: sha, keys: ['stratum', 'tags', '(key)'] },
       { rule: 'sealed.label_join', file: 'k.jsonl', commit: sha, keys: ['stratum', '(key)'] },
       { rule: 'sealed.label_join', file: 'm.tsv', commit: sha, keys: ['stratum', 'head'] },
+      { rule: 'sealed.label_join', file: 'n.csv', commit: sha, keys: ['stratum', 'head'] },
     ]);
   });