diff --git a/UPGRADE-4.3.md b/UPGRADE-4.3.md
index a6a1f73afb..2e6c64b2b9 100644
--- a/UPGRADE-4.3.md
+++ b/UPGRADE-4.3.md
@@ -4,6 +4,7 @@ UPGRADE FROM 4.2 to 4.3
 BrowserKit
 ----------
 
+ * Deprecated `Response::buildHeader()`
  * Deprecated `Response::getStatus()`, use `Response::getStatusCode()` instead
 
 Config
diff --git a/UPGRADE-5.0.md b/UPGRADE-5.0.md
index ad9e6535a8..f1acd19eff 100644
--- a/UPGRADE-5.0.md
+++ b/UPGRADE-5.0.md
@@ -4,6 +4,7 @@ UPGRADE FROM 4.x to 5.0
 BrowserKit
 ----------
 
+ * Removed `Response::buildHeader()`
  * Removed `Response::getStatus()`, use `Response::getStatusCode()` instead
  * The `Client::submit()` method has a new `$serverParameters` argument.
 
diff --git a/src/Symfony/Component/BrowserKit/CHANGELOG.md b/src/Symfony/Component/BrowserKit/CHANGELOG.md
index 55a8d7d518..37a724261a 100644
--- a/src/Symfony/Component/BrowserKit/CHANGELOG.md
+++ b/src/Symfony/Component/BrowserKit/CHANGELOG.md
@@ -4,6 +4,7 @@ CHANGELOG
 4.3.0
 -----
 
+ * Deprecated `Response::buildHeader()`
  * Deprecated `Response::getStatus()`, use `Response::getStatusCode()` instead
 
 4.2.0
diff --git a/src/Symfony/Component/BrowserKit/Response.php b/src/Symfony/Component/BrowserKit/Response.php
index 711e4d1aac..9045da5673 100644
--- a/src/Symfony/Component/BrowserKit/Response.php
+++ b/src/Symfony/Component/BrowserKit/Response.php
@@ -45,10 +45,10 @@ class Response
         $headers = '';
         foreach ($this->headers as $name => $value) {
             if (\is_string($value)) {
-                $headers .= $this->buildHeader($name, $value);
+                $headers .= sprintf("%s: %s\n", $name, $value);
             } else {
                 foreach ($value as $headerValue) {
-                    $headers .= $this->buildHeader($name, $headerValue);
+                    $headers .= sprintf("%s: %s\n", $name, $headerValue);
                 }
             }
         }
@@ -63,9 +63,13 @@ class Response
      * @param string $value The header value
      *
      * @return string The built header line
+     *
+     * @deprecated since Symfony 4.3
      */
     protected function buildHeader($name, $value)
     {
+        @trigger_error(sprintf('The "%s()" method is deprecated since Symfony 4.3.', __METHOD__), E_USER_DEPRECATED);
+
         return sprintf("%s: %s\n", $name, $value);
     }