diff --git a/plugin/test/fixtures/v4/functions-without-gatsby-plugin/e2e-tests/test-helpers.js b/plugin/test/fixtures/v4/functions-without-gatsby-plugin/e2e-tests/test-helpers.js
index f4a7d3d4..23228678 100644
--- a/plugin/test/fixtures/v4/functions-without-gatsby-plugin/e2e-tests/test-helpers.js
+++ b/plugin/test/fixtures/v4/functions-without-gatsby-plugin/e2e-tests/test-helpers.js
@@ -115,7 +115,7 @@ exports.runTests = function runTests(env, host) {
         expect(result).toEqual({
           amIJSON: true,
         })
-        expect(res.headers.get('content-type')).toEqual('application/json')
+        expect(res.headers.get('content-type')).toMatch(/^application\/json/)
       })
       test(`returns json correctly via send`, async () => {
         const res = await fetchTwice(`${host}/api/i-am-json-too`)
@@ -124,14 +124,14 @@ exports.runTests = function runTests(env, host) {
         expect(result).toEqual({
           amIJSON: true,
         })
-        expect(res.headers.get('content-type')).toEqual('application/json')
+        expect(res.headers.get('content-type')).toMatch(/^application\/json/)
       })
       test(`returns boolean correctly via send`, async () => {
         const res = await fetchTwice(`${host}/api/i-am-false`)
         const result = await res.json()
 
         expect(result).toEqual(false)
-        expect(res.headers.get('content-type')).toEqual('application/json')
+        expect(res.headers.get('content-type')).toMatch(/^application\/json/)
       })
       test(`returns status correctly via send`, async () => {
         const res = await fetchTwice(`${host}/api/i-am-status`)
diff --git a/plugin/test/fixtures/v5/functions-without-gatsby-plugin/e2e-tests/test-helpers.js b/plugin/test/fixtures/v5/functions-without-gatsby-plugin/e2e-tests/test-helpers.js
index f4a7d3d4..23228678 100644
--- a/plugin/test/fixtures/v5/functions-without-gatsby-plugin/e2e-tests/test-helpers.js
+++ b/plugin/test/fixtures/v5/functions-without-gatsby-plugin/e2e-tests/test-helpers.js
@@ -115,7 +115,7 @@ exports.runTests = function runTests(env, host) {
         expect(result).toEqual({
           amIJSON: true,
         })
-        expect(res.headers.get('content-type')).toEqual('application/json')
+        expect(res.headers.get('content-type')).toMatch(/^application\/json/)
       })
       test(`returns json correctly via send`, async () => {
         const res = await fetchTwice(`${host}/api/i-am-json-too`)
@@ -124,14 +124,14 @@ exports.runTests = function runTests(env, host) {
         expect(result).toEqual({
           amIJSON: true,
         })
-        expect(res.headers.get('content-type')).toEqual('application/json')
+        expect(res.headers.get('content-type')).toMatch(/^application\/json/)
       })
       test(`returns boolean correctly via send`, async () => {
         const res = await fetchTwice(`${host}/api/i-am-false`)
         const result = await res.json()
 
         expect(result).toEqual(false)
-        expect(res.headers.get('content-type')).toEqual('application/json')
+        expect(res.headers.get('content-type')).toMatch(/^application\/json/)
       })
       test(`returns status correctly via send`, async () => {
         const res = await fetchTwice(`${host}/api/i-am-status`)
diff --git a/plugin/test/fixtures/v5/with-adapters/e2e-tests/test-helpers.js b/plugin/test/fixtures/v5/with-adapters/e2e-tests/test-helpers.js
index 30b4d1ea..437f1f69 100644
--- a/plugin/test/fixtures/v5/with-adapters/e2e-tests/test-helpers.js
+++ b/plugin/test/fixtures/v5/with-adapters/e2e-tests/test-helpers.js
@@ -117,7 +117,7 @@ exports.runTests = function runTests(env, host) {
         expect(result).toEqual({
           amIJSON: true,
         })
-        expect(res.headers.get('content-type')).toEqual('application/json')
+        expect(res.headers.get('content-type')).toMatch(/^application\/json/)
       })
       test(`returns json correctly via send`, async () => {
         const res = await fetchTwice(`${host}/api/i-am-json-too`)
@@ -126,14 +126,14 @@ exports.runTests = function runTests(env, host) {
         expect(result).toEqual({
           amIJSON: true,
         })
-        expect(res.headers.get('content-type')).toEqual('application/json')
+        expect(res.headers.get('content-type')).toMatch(/^application\/json/)
       })
       test(`returns boolean correctly via send`, async () => {
         const res = await fetchTwice(`${host}/api/i-am-false`)
         const result = await res.json()
 
         expect(result).toEqual(false)
-        expect(res.headers.get('content-type')).toEqual('application/json')
+        expect(res.headers.get('content-type')).toMatch(/^application\/json/)
       })
       test(`returns status correctly via send`, async () => {
         const res = await fetchTwice(`${host}/api/i-am-status`)