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fix: prevent Content-Type header from being set to 'false' #7035

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fix: prevent Content-Type header from being set to 'false' #7035

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a00eb83
fix: prevent Content-Type header from being set to 'false'
veeceey Feb 14, 2026
eed5db6
Merge branch 'master' into fix/content-type-false-value
veeceey Feb 19, 2026
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2 changes: 1 addition & 1 deletion lib/response.js
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Original file line number Diff line number Diff line change
Expand Up @@ -673,7 +673,7 @@ res.header = function header(field, val) {
if (Array.isArray(value)) {
throw new TypeError('Content-Type cannot be set to an Array');
}
value = mime.contentType(value)
value = mime.contentType(value) || value
}

this.setHeader(field, value);
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14 changes: 14 additions & 0 deletions test/res.set.js
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Expand Up @@ -31,6 +31,20 @@ describe('res', function(){
.expect('X-Number', '123')
.expect(200, 'string', done);
})

it('should preserve Content-Type value when mime lookup fails', function (done) {
var app = express();

app.use(function (req, res) {
res.set('Content-Type', 'custom-type');
res.end();
});

request(app)
.get('/')
.expect('Content-Type', 'custom-type')
.expect(200, done);
})
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@GroophyLifefor GroophyLifefor Feb 24, 2026

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Suggested change
})
})
it('should preserve Content-Type value when mime lookup fails even has slash', function (done) {
var app = express();
app.use(function (req, res) {
res.set('Content-Type', 'custom-type/subtype');
res.end();
});
request(app)
.get('/')
.expect('Content-Type', 'custom-type/subtype')
.expect(200, done);
})

Since MIME types are closely related to slash based formats, adding a test case that includes a slash helps catch potential production issues before release.

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@krzysdz krzysdz Feb 24, 2026

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If the string passed to mime.contentType() contains a /, then it is treated as a mime type and returned as is (ref).

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@GroophyLifefor GroophyLifefor Feb 24, 2026

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Good catch, that makes my additional test is unnecessary, thank you.

})

describe('.set(field, values)', function(){
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