diff --git a/trac/web/api.py b/trac/web/api.py
index b2e76f948..062c46550 100644
--- a/trac/web/api.py
+++ b/trac/web/api.py
@@ -605,6 +605,7 @@ class Request(object):
         """Must be called after all headers have been sent and before the
         actual content is written.
         """
+        self._send_configurable_headers()
         self._send_cookie_headers()
         self._write = self._start_response(self._status, self._outheaders)
 
@@ -725,6 +726,7 @@ class Request(object):
         self.send_header('Expires', 'Fri, 01 Jan 1999 00:00:00 GMT')
         self.send_header('Content-Type', content_type + ';charset=utf-8')
         self.send_header('Content-Length', len(data))
+        self._send_configurable_headers()
         self._send_cookie_headers()
 
         self._write = self._start_response(self._status, self._outheaders,
@@ -947,6 +949,10 @@ class Request(object):
         return urlparse.urlunparse((self.scheme, host, self.base_path, None,
                                     None, None))
 
+    def _send_configurable_headers(self):
+        for name, val in getattr(self, 'configurable_headers', []):
+            self.send_header(name, val)
+
     def _send_cookie_headers(self):
         for name in self.outcookie.keys():
             path = self.outcookie[name].get('path')
diff --git a/trac/web/main.py b/trac/web/main.py
index 56b493d38..4008d7e77 100644
--- a/trac/web/main.py
+++ b/trac/web/main.py
@@ -38,8 +38,9 @@ from genshi.output import DocType
 from genshi.template import TemplateLoader
 
 from trac import __version__ as TRAC_VERSION
-from trac.config import BoolOption, ChoiceOption, ConfigurationError, \
-                        ExtensionOption, Option, OrderedExtensionsOption
+from trac.config import (
+    BoolOption, ChoiceOption, ConfigSection, ConfigurationError,
+    ExtensionOption, Option, OrderedExtensionsOption)
 from trac.core import *
 from trac.env import open_environment
 from trac.loader import get_plugin_info, match_plugins_to_frames
@@ -164,6 +165,10 @@ class RequestDispatcher(Component):
         """The header to use if `use_xsendfile` is enabled. If Nginx is used,
         set `X-Accel-Redirect`. (''since 1.0.6'')""")
 
+    configurable_headers = ConfigSection('http-headers', """
+        Headers to be added to the HTTP request. (''since 1.2.3'')
+        """)
+
     # Public API
 
     def authenticate(self, req):
@@ -317,6 +322,7 @@ class RequestDispatcher(Component):
             'tz': self._get_timezone,
             'use_xsendfile': self._get_use_xsendfile,
             'xsendfile_header': self._get_xsendfile_header,
+            'configurable_headers': self._get_configurable_headers,
         })
 
     @lazy
@@ -412,12 +418,12 @@ class RequestDispatcher(Component):
         return self.use_xsendfile
 
     # RFC7230 3.2 Header Fields
-    _xsendfile_header_re = re.compile(r"[-0-9A-Za-z!#$%&'*+.^_`|~]+\Z")
+    _valid_header_re = re.compile(r"[-0-9A-Za-z!#$%&'*+.^_`|~]+\Z")
     _warn_xsendfile_header = False
 
     def _get_xsendfile_header(self, req):
         header = self.xsendfile_header.strip()
-        if self._xsendfile_header_re.match(header):
+        if self._valid_header_re.match(header):
             return to_utf8(header)
         else:
             if not self._warn_xsendfile_header:
@@ -426,6 +432,29 @@ class RequestDispatcher(Component):
                               header)
             return None
 
+    _control_codes_re = re.compile(r'[\x00-\x08\x0a-\x1f\x7f]')
+    _reserverd_headers = set(['content-type', 'content-length', 'location',
+                              'etag', 'pragma', 'cache-control', 'expires'])
+
+    @lazy
+    def _configurable_headers(self):
+        headers = []
+        invalids = []
+        for name, val in self.configurable_headers.options():
+            if name and name.lower() not in self._reserverd_headers and \
+                    self._valid_header_re.match(name) and \
+                    not self._control_codes_re.search(val):
+                headers.append((name, val))
+            else:
+                invalids.append((name, val))
+        if invalids:
+            self.log.warning('[http-headers] invalid headers are ignored: %r',
+                             invalids)
+        return tuple(headers)
+
+    def _get_configurable_headers(self, req):
+        return iter(self._configurable_headers)
+
     def _pre_process_request(self, req, chosen_handler):
         for filter_ in self.filters:
             chosen_handler = filter_.pre_process_request(req, chosen_handler)