diff --git a/src/LinkBuilder/LinkBuilder.php b/src/LinkBuilder/LinkBuilder.php
index 1793e50..6febfab 100644
--- a/src/LinkBuilder/LinkBuilder.php
+++ b/src/LinkBuilder/LinkBuilder.php
@@ -38,6 +38,13 @@ public function asUrl(): string
   {
     $scheme = $this->_scheme ?? ($this->_request->isSecure(true) ? 'https' : 'http');
     $port = $this->_port ?? $this->_request->port();
+
+    // When the scheme comes from a proxy that terminated tls, the port the
+    // request arrived on is the proxy's, not the one the url is reachable on
+    $schemeIsForwarded = $this->_scheme === null
+      && $this->_port === null
+      && $this->_request->isSecure(true)
+      && !$this->_request->isSecure();
     return
       ($scheme . '://') . implode(
         '.',
@@ -47,7 +54,7 @@ public function asUrl(): string
           ($this->_tld ?? $this->_request->tld()),
         ]
       )
-      . ($this->_isStandardPort($this->_scheme ?? $this->_request->getScheme(), $port) ? '' : ':' . $port)
+      . ($schemeIsForwarded || $this->_isStandardPort($scheme, $port) ? '' : ':' . $port)
       . (isset($this->_path[0]) && $this->_path[0] !== '/' ? '/' : '')
       . $this->_path
       . (!empty($this->_query) ? '?' . http_build_query($this->_query) : null)
diff --git a/tests/LinkBuilderTest.php b/tests/LinkBuilderTest.php
index 4932140..544d0ba 100644
--- a/tests/LinkBuilderTest.php
+++ b/tests/LinkBuilderTest.php
@@ -83,4 +83,21 @@ public function testAsUrl()
     $lb->setFragment('def');
     self::assertEquals('https://secure.packaged.local#def', $lb->asUrl());
   }
+
+  /**
+   * Behind a TLS terminating proxy the scheme comes from X-Forwarded-Proto, so
+   * 443 is the standard port and should not be written into the url
+   */
+  public function testAsUrlBehindTlsTerminatingProxy()
+  {
+    $request = Request::create('http://www.packaged.local:443/');
+    $request->headers->set('X_FORWARDED_PROTO', 'https');
+
+    self::assertFalse($request->isSecure());
+    self::assertTrue($request->isSecure(true));
+    self::assertEquals('http', $request->getScheme());
+    self::assertEquals(443, $request->port());
+
+    self::assertEquals('https://www.packaged.local', LinkBuilder::fromRequest($request)->asUrl());
+  }
 }