diff --git a/push/include/prometheus/gateway.h b/push/include/prometheus/gateway.h
index e6acd0f0..b65cfb28 100644
--- a/push/include/prometheus/gateway.h
+++ b/push/include/prometheus/gateway.h
@@ -58,6 +58,12 @@ class PROMETHEUS_CPP_PUSH_EXPORT Gateway {
   // Delete metrics from the given pushgateway (for configured instance labels).
   std::future<int> AsyncDeleteForInstance();
 
+  /// \brief Add a custom HTTP header.
+  ///
+  /// \param header custom header in the form "key:value".
+  /// \return true on success, otherwise false
+  bool AddHttpHeader(const std::string& header);
+
  private:
   std::string jobUri_;
   std::string labels_;
diff --git a/push/src/curl_wrapper.cc b/push/src/curl_wrapper.cc
index 767e10f1..8481c47a 100644
--- a/push/src/curl_wrapper.cc
+++ b/push/src/curl_wrapper.cc
@@ -22,12 +22,18 @@ CurlWrapper::CurlWrapper(const std::string& username,
     throw std::runtime_error("Cannot initialize easy curl!");
   }
 
+  optHttpHeader_ = curl_slist_append(nullptr, CONTENT_TYPE);
+  if (!optHttpHeader_) {
+    throw std::runtime_error("Cannot append the header of the content type");
+  }
+
   if (!username.empty()) {
     auth_ = username + ":" + password;
   }
 }
 
 CurlWrapper::~CurlWrapper() {
+  curl_slist_free_all(optHttpHeader_);
   curl_easy_cleanup(curl_);
   curl_global_cleanup();
 }
@@ -39,9 +45,7 @@ int CurlWrapper::performHttpRequest(HttpMethod method, const std::string& uri,
   curl_easy_reset(curl_);
   curl_easy_setopt(curl_, CURLOPT_URL, uri.c_str());
 
-  curl_slist* header_chunk = nullptr;
-  header_chunk = curl_slist_append(header_chunk, CONTENT_TYPE);
-  curl_easy_setopt(curl_, CURLOPT_HTTPHEADER, header_chunk);
+  curl_easy_setopt(curl_, CURLOPT_HTTPHEADER, optHttpHeader_);
 
   if (!body.empty()) {
     curl_easy_setopt(curl_, CURLOPT_POSTFIELDSIZE, body.size());
@@ -77,8 +81,6 @@ int CurlWrapper::performHttpRequest(HttpMethod method, const std::string& uri,
   long response_code;
   curl_easy_getinfo(curl_, CURLINFO_RESPONSE_CODE, &response_code);
 
-  curl_slist_free_all(header_chunk);
-
   if (curl_error != CURLE_OK) {
     return -curl_error;
   }
@@ -86,5 +88,16 @@ int CurlWrapper::performHttpRequest(HttpMethod method, const std::string& uri,
   return response_code;
 }
 
+bool CurlWrapper::addHttpHeader(const std::string& header) {
+  std::lock_guard<std::mutex> lock{mutex_};
+  auto updated_header = curl_slist_append(optHttpHeader_, header.c_str());
+  if (!updated_header) {
+    return false;
+  }
+
+  optHttpHeader_ = updated_header;
+  return true;
+}
+
 }  // namespace detail
 }  // namespace prometheus
diff --git a/push/src/curl_wrapper.h b/push/src/curl_wrapper.h
index df20d6bb..e62c62f8 100644
--- a/push/src/curl_wrapper.h
+++ b/push/src/curl_wrapper.h
@@ -21,11 +21,13 @@ class CurlWrapper {
 
   int performHttpRequest(HttpMethod method, const std::string& uri,
                          const std::string& body);
+  bool addHttpHeader(const std::string& header);
 
  private:
   CURL* curl_;
   std::string auth_;
   std::mutex mutex_;
+  curl_slist* optHttpHeader_;
 };
 
 }  // namespace detail
diff --git a/push/src/gateway.cc b/push/src/gateway.cc
index 7d61266c..e1ec9d5d 100644
--- a/push/src/gateway.cc
+++ b/push/src/gateway.cc
@@ -164,4 +164,8 @@ void Gateway::CleanupStalePointers(
       std::end(collectables));
 }
 
+bool Gateway::AddHttpHeader(const std::string& header) {
+  return curlWrapper_->addHttpHeader(header);
+}
+
 }  // namespace prometheus