diff --git a/src/ControllerMethod.php b/src/ControllerMethod.php
index 7ee1bf8..0dad47e 100644
--- a/src/ControllerMethod.php
+++ b/src/ControllerMethod.php
@@ -26,6 +26,262 @@
 class ControllerMethod {
 	private const STATUS_CODE_DESCRIPTION_PATTERN = '/^(\d{3}): (.+)$/';
 
+	// Generate the list using this command:
+	// curl https://www.iana.org/assignments/http-fields/field-names.csv | cut -d ',' -f 1 | tail -n +2 | head -n -1 | tr '[:upper:]' '[:lower:]' | grep -E '^[a-z]' | sed -e "s/^/'/g" | sed -e "s/$/',/g"
+	private const HTTP_STANDARD_HEADERS = [
+		'a-im',
+		'accept',
+		'accept-additions',
+		'accept-ch',
+		'accept-charset',
+		'accept-datetime',
+		'accept-encoding',
+		'accept-features',
+		'accept-language',
+		'accept-patch',
+		'accept-post',
+		'accept-ranges',
+		'accept-signature',
+		'access-control',
+		'access-control-allow-credentials',
+		'access-control-allow-headers',
+		'access-control-allow-methods',
+		'access-control-allow-origin',
+		'access-control-expose-headers',
+		'access-control-max-age',
+		'access-control-request-headers',
+		'access-control-request-method',
+		'activate-storage-access',
+		'age',
+		'allow',
+		'alpn',
+		'alt-svc',
+		'alt-used',
+		'alternates',
+		'amp-cache-transform',
+		'apply-to-redirect-ref',
+		'authentication-control',
+		'authentication-info',
+		'authorization',
+		'available-dictionary',
+		'c-ext',
+		'c-man',
+		'c-opt',
+		'c-pep',
+		'c-pep-info',
+		'cache-control',
+		'cache-group-invalidation',
+		'cache-groups',
+		'cache-status',
+		'cal-managed-id',
+		'caldav-timezones',
+		'capsule-protocol',
+		'cdn-cache-control',
+		'cdn-loop',
+		'cert-not-after',
+		'cert-not-before',
+		'clear-site-data',
+		'client-cert',
+		'client-cert-chain',
+		'close',
+		'cmcd-object',
+		'cmcd-request',
+		'cmcd-session',
+		'cmcd-status',
+		'cmsd-dynamic',
+		'cmsd-static',
+		'concealed-auth-export',
+		'configuration-context',
+		'connection',
+		'content-base',
+		'content-digest',
+		'content-disposition',
+		'content-encoding',
+		'content-id',
+		'content-language',
+		'content-length',
+		'content-location',
+		'content-md5',
+		'content-range',
+		'content-script-type',
+		'content-security-policy',
+		'content-security-policy-report-only',
+		'content-style-type',
+		'content-type',
+		'content-version',
+		'cookie',
+		'cookie2',
+		'cross-origin-embedder-policy',
+		'cross-origin-embedder-policy-report-only',
+		'cross-origin-opener-policy',
+		'cross-origin-opener-policy-report-only',
+		'cross-origin-resource-policy',
+		'cta-common-access-token',
+		'dasl',
+		'date',
+		'dav',
+		'default-style',
+		'delta-base',
+		'deprecation',
+		'depth',
+		'derived-from',
+		'destination',
+		'detached-jws',
+		'differential-id',
+		'dictionary-id',
+		'digest',
+		'dpop',
+		'dpop-nonce',
+		'early-data',
+		'ediint-features',
+		'etag',
+		'expect',
+		'expect-ct',
+		'expires',
+		'ext',
+		'forwarded',
+		'from',
+		'getprofile',
+		'hobareg',
+		'host',
+		'http2-settings',
+		'if',
+		'if-match',
+		'if-modified-since',
+		'if-none-match',
+		'if-range',
+		'if-schedule-tag-match',
+		'if-unmodified-since',
+		'im',
+		'include-referred-token-binding-id',
+		'isolation',
+		'keep-alive',
+		'label',
+		'last-event-id',
+		'last-modified',
+		'link',
+		'link-template',
+		'location',
+		'lock-token',
+		'man',
+		'max-forwards',
+		'memento-datetime',
+		'meter',
+		'method-check',
+		'method-check-expires',
+		'mime-version',
+		'negotiate',
+		'nel',
+		'odata-entityid',
+		'odata-isolation',
+		'odata-maxversion',
+		'odata-version',
+		'opt',
+		'optional-www-authenticate',
+		'ordering-type',
+		'origin',
+		'origin-agent-cluster',
+		'oscore',
+		'oslc-core-version',
+		'overwrite',
+		'p3p',
+		'pep',
+		'pep-info',
+		'permissions-policy',
+		'pics-label',
+		'ping-from',
+		'ping-to',
+		'position',
+		'pragma',
+		'prefer',
+		'preference-applied',
+		'priority',
+		'profileobject',
+		'protocol',
+		'protocol-info',
+		'protocol-query',
+		'protocol-request',
+		'proxy-authenticate',
+		'proxy-authentication-info',
+		'proxy-authorization',
+		'proxy-features',
+		'proxy-instruction',
+		'proxy-status',
+		'public',
+		'public-key-pins',
+		'public-key-pins-report-only',
+		'range',
+		'redirect-ref',
+		'referer',
+		'referer-root',
+		'referrer-policy',
+		'refresh',
+		'repeatability-client-id',
+		'repeatability-first-sent',
+		'repeatability-request-id',
+		'repeatability-result',
+		'replay-nonce',
+		'reporting-endpoints',
+		'repr-digest',
+		'retry-after',
+		'safe',
+		'schedule-reply',
+		'schedule-tag',
+		'sec-fetch-dest',
+		'sec-fetch-mode',
+		'sec-fetch-site',
+		'sec-fetch-storage-access',
+		'sec-fetch-user',
+		'sec-gpc',
+		'sec-purpose',
+		'sec-token-binding',
+		'sec-websocket-accept',
+		'sec-websocket-extensions',
+		'sec-websocket-key',
+		'sec-websocket-protocol',
+		'sec-websocket-version',
+		'security-scheme',
+		'server',
+		'server-timing',
+		'set-cookie',
+		'set-cookie2',
+		'setprofile',
+		'signature',
+		'signature-input',
+		'slug',
+		'soapaction',
+		'status-uri',
+		'strict-transport-security',
+		'sunset',
+		'surrogate-capability',
+		'surrogate-control',
+		'tcn',
+		'te',
+		'timeout',
+		'timing-allow-origin',
+		'topic',
+		'traceparent',
+		'tracestate',
+		'trailer',
+		'transfer-encoding',
+		'ttl',
+		'upgrade',
+		'urgency',
+		'uri',
+		'use-as-dictionary',
+		'user-agent',
+		'variant-vary',
+		'vary',
+		'via',
+		'want-content-digest',
+		'want-digest',
+		'want-repr-digest',
+		'warning',
+		'www-authenticate',
+		'x-content-type-options',
+		'x-frame-options',
+	];
+
 	/**
 	 * @param ControllerMethodParameter[] $parameters
 	 * @param array<string, string> $requestHeaders
@@ -301,7 +557,15 @@ public static function parse(string $context,
 				$methodCall->var->var->name === 'this' &&
 				$methodCall->var->name->name === 'request') {
 				if ($methodCall->name->name === 'getHeader') {
-					$codeRequestHeaders[] = $methodCall->args[0]->value->value;
+					$headerName = self::cleanHeaderName($methodCall->args[0]->value->value);
+
+					if ($headerName !== $methodCall->args[0]->value->value) {
+						Logger::error($context, 'Request header "' . $methodCall->args[0]->value->value . '" should be "' . $headerName . '".');
+					}
+
+					self::checkCustomHeaderName($context, $headerName);
+
+					$codeRequestHeaders[] = $headerName;
 				}
 				if ($methodCall->name->name === 'getParam') {
 					$name = $methodCall->args[0]->value->value;
@@ -352,11 +616,18 @@ public static function parse(string $context,
 						$args[$attrName] = $arg->value->value;
 					}
 
-					if (array_key_exists($args['name'], $attributeRequestHeaders)) {
-						Logger::error($context, 'Request header "' . $args['name'] . '" already documented.');
+					$headerName = self::cleanHeaderName($args['name']);
+					if ($headerName !== $args['name']) {
+						Logger::error($context, 'Request header "' . $args['name'] . '" should be "' . $headerName . '".');
+					}
+
+					self::checkCustomHeaderName($context, $headerName);
+
+					if (array_key_exists($headerName, $attributeRequestHeaders)) {
+						Logger::error($context, 'Request header "' . $headerName . '" already documented.');
 					}
 
-					$attributeRequestHeaders[$args['name']] = $args['description'];
+					$attributeRequestHeaders[$headerName] = $args['description'];
 				}
 			}
 		}
@@ -377,4 +648,17 @@ public static function parse(string $context,
 		return new ControllerMethod($parameters, $attributeRequestHeaders, $responses, $responseDescriptions, $methodDescription, $methodSummary, $isDeprecated);
 	}
 
+	private static function cleanHeaderName(string $header): string {
+		return str_replace('_', '-', strtolower($header));
+	}
+
+	private static function checkCustomHeaderName(string $context, string $header): void {
+		if (in_array($header, self::HTTP_STANDARD_HEADERS, true)) {
+			return;
+		}
+
+		if (!str_starts_with($header, 'x-')) {
+			Logger::warning($context, 'Request header "' . $header . '" should start with "x-" to denote a custom header.');
+		}
+	}
 }
diff --git a/tests/lib/Controller/SettingsController.php b/tests/lib/Controller/SettingsController.php
index e370757..6498ca0 100644
--- a/tests/lib/Controller/SettingsController.php
+++ b/tests/lib/Controller/SettingsController.php
@@ -760,16 +760,18 @@ public function samePathPost(): DataResponse {
 	 *
 	 * 200: Admin settings updated
 	 */
-	#[RequestHeader('X-Custom-Header-1', 'A custom header 1')]
-	#[RequestHeader('X-Custom-Header-2', description: 'A custom header 2')]
-	#[RequestHeader(name: 'X-Custom-Header-3', description: 'A custom header 3')]
-	#[RequestHeader(description: 'A custom header 4', name: 'X-Custom-Header-4')]
+	#[RequestHeader('x-custom-header-1', 'A custom header 1')]
+	#[RequestHeader('x-custom-header-2', description: 'A custom header 2')]
+	#[RequestHeader(name: 'x-custom-header-3', description: 'A custom header 3')]
+	#[RequestHeader(description: 'A custom header 4', name: 'x-custom-header-4')]
 	public function requestHeader(): DataResponse {
-		$this->request->getHeader('X-Custom-Header-1');
-		$this->request->getHeader('X-Custom-Header-2');
-		$this->request->getHeader('X-Custom-Header-3');
-		$this->request->getHeader('X-Custom-Header-4');
-		$this->request->getHeader('X-Custom-Header-5');
+		$this->request->getHeader('x-custom-header-1');
+		$this->request->getHeader('x-custom-header-2');
+		$this->request->getHeader('x-custom-header-3');
+		$this->request->getHeader('x-custom-header-4');
+		$this->request->getHeader('x-custom-header-5');
+		$this->request->getHeader('custom-header-6');
+		$this->request->getHeader('user-agent');
 
 		return new DataResponse();
 	}
diff --git a/tests/openapi-administration.json b/tests/openapi-administration.json
index 70a66d1..24f9a83 100644
--- a/tests/openapi-administration.json
+++ b/tests/openapi-administration.json
@@ -5472,7 +5472,7 @@
                         }
                     },
                     {
-                        "name": "X-Custom-Header-1",
+                        "name": "x-custom-header-1",
                         "in": "header",
                         "description": "A custom header 1",
                         "schema": {
@@ -5480,7 +5480,7 @@
                         }
                     },
                     {
-                        "name": "X-Custom-Header-2",
+                        "name": "x-custom-header-2",
                         "in": "header",
                         "description": "A custom header 2",
                         "schema": {
@@ -5488,7 +5488,7 @@
                         }
                     },
                     {
-                        "name": "X-Custom-Header-3",
+                        "name": "x-custom-header-3",
                         "in": "header",
                         "description": "A custom header 3",
                         "schema": {
@@ -5496,7 +5496,7 @@
                         }
                     },
                     {
-                        "name": "X-Custom-Header-4",
+                        "name": "x-custom-header-4",
                         "in": "header",
                         "description": "A custom header 4",
                         "schema": {
@@ -5504,7 +5504,21 @@
                         }
                     },
                     {
-                        "name": "X-Custom-Header-5",
+                        "name": "x-custom-header-5",
+                        "in": "header",
+                        "schema": {
+                            "type": "string"
+                        }
+                    },
+                    {
+                        "name": "custom-header-6",
+                        "in": "header",
+                        "schema": {
+                            "type": "string"
+                        }
+                    },
+                    {
+                        "name": "user-agent",
                         "in": "header",
                         "schema": {
                             "type": "string"
diff --git a/tests/openapi-full.json b/tests/openapi-full.json
index d9cc871..4e6955f 100644
--- a/tests/openapi-full.json
+++ b/tests/openapi-full.json
@@ -5629,7 +5629,7 @@
                         }
                     },
                     {
-                        "name": "X-Custom-Header-1",
+                        "name": "x-custom-header-1",
                         "in": "header",
                         "description": "A custom header 1",
                         "schema": {
@@ -5637,7 +5637,7 @@
                         }
                     },
                     {
-                        "name": "X-Custom-Header-2",
+                        "name": "x-custom-header-2",
                         "in": "header",
                         "description": "A custom header 2",
                         "schema": {
@@ -5645,7 +5645,7 @@
                         }
                     },
                     {
-                        "name": "X-Custom-Header-3",
+                        "name": "x-custom-header-3",
                         "in": "header",
                         "description": "A custom header 3",
                         "schema": {
@@ -5653,7 +5653,7 @@
                         }
                     },
                     {
-                        "name": "X-Custom-Header-4",
+                        "name": "x-custom-header-4",
                         "in": "header",
                         "description": "A custom header 4",
                         "schema": {
@@ -5661,7 +5661,21 @@
                         }
                     },
                     {
-                        "name": "X-Custom-Header-5",
+                        "name": "x-custom-header-5",
+                        "in": "header",
+                        "schema": {
+                            "type": "string"
+                        }
+                    },
+                    {
+                        "name": "custom-header-6",
+                        "in": "header",
+                        "schema": {
+                            "type": "string"
+                        }
+                    },
+                    {
+                        "name": "user-agent",
                         "in": "header",
                         "schema": {
                             "type": "string"