diff --git a/CHANGELOG.md b/CHANGELOG.md
index daa351e51d..651c54da10 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,9 @@ For experimental package changes, see the [experimental CHANGELOG](experimental/
 
 ### :bug: (Bug Fix)
 
+* fix(otlp-proto-exporter-base): Match Accept header with Content-Type in the proto exporter
+ [#3562](https://github.com/open-telemetry/opentelemetry-js/pull/3562) @scheler
+
 ### :books: (Refine Doc)
 
 ### :house: (Internal)
diff --git a/experimental/packages/otlp-proto-exporter-base/scripts/protos.js b/experimental/packages/otlp-proto-exporter-base/scripts/protos.js
index e06cc9db44..3f3fbd6c0c 100644
--- a/experimental/packages/otlp-proto-exporter-base/scripts/protos.js
+++ b/experimental/packages/otlp-proto-exporter-base/scripts/protos.js
@@ -45,6 +45,7 @@ async function pbjs(files) {
   const outFile = path.join(generatedPath, 'root.js');
   const pbjsOptions = [
     '-t', 'static-module',
+    '-p', protosPath,
     '-w', 'commonjs',
     '--null-defaults',
     '-o', outFile,
diff --git a/experimental/packages/otlp-proto-exporter-base/src/platform/browser/OTLPProtoExporterBrowserBase.ts b/experimental/packages/otlp-proto-exporter-base/src/platform/browser/OTLPProtoExporterBrowserBase.ts
index 1b386855e4..4e9f95d5c0 100644
--- a/experimental/packages/otlp-proto-exporter-base/src/platform/browser/OTLPProtoExporterBrowserBase.ts
+++ b/experimental/packages/otlp-proto-exporter-base/src/platform/browser/OTLPProtoExporterBrowserBase.ts
@@ -75,7 +75,11 @@ export abstract class OTLPProtoExporterBrowserBase<
         sendWithXhr(
           new Blob([body], { type: 'application/x-protobuf' }),
           this.url,
-          { ...this._headers, 'Content-Type': 'application/x-protobuf' },
+          {
+            ...this._headers,
+            'Content-Type': 'application/x-protobuf',
+            Accept: 'application/x-protobuf',
+          },
           this.timeoutMillis,
           onSuccess,
           onError
diff --git a/experimental/packages/otlp-transformer/package.json b/experimental/packages/otlp-transformer/package.json
index ba4462f5c5..cd1641edcc 100644
--- a/experimental/packages/otlp-transformer/package.json
+++ b/experimental/packages/otlp-transformer/package.json
@@ -66,7 +66,7 @@
     "karma-mocha": "2.0.1",
     "karma-spec-reporter": "0.0.32",
     "karma-webpack": "4.0.2",
-    "mkdirp": "1.0.4",
+    "mkdirp": "2.1.3",
     "mocha": "10.0.0",
     "nyc": "15.1.0",
     "rimraf": "3.0.2",