diff --git a/src/wp-includes/media.php b/src/wp-includes/media.php
index 0a8621d209815..f79ce679f6770 100644
--- a/src/wp-includes/media.php
+++ b/src/wp-includes/media.php
@@ -1366,13 +1366,17 @@ function wp_calculate_image_srcset( $size_array, $image_src, $image_meta, $attac
 	 * (which is to say, when they share the domain name of the current request).
 	 */
 	if ( is_ssl() && ! str_starts_with( $image_baseurl, 'https' ) ) {
-		// Since the `Host:` header might contain a port we should
-		// compare it against the image URL using the same port.
+		/*
+		 * Since the `Host:` header might contain a port, it should
+		 * be compared against the image URL using the same port.
+		 */
 		$parsed = parse_url( $image_baseurl );
-		$domain = $parsed['host'];
+		$domain = isset( $parsed['host'] ) ? $parsed['host'] : '';
+
 		if ( isset( $parsed['port'] ) ) {
 			$domain .= ':' . $parsed['port'];
 		}
+
 		if ( $_SERVER['HTTP_HOST'] === $domain ) {
 			$image_baseurl = set_url_scheme( $image_baseurl, 'https' );
 		}
diff --git a/tests/phpunit/tests/media.php b/tests/phpunit/tests/media.php
index 22d7d7a441a67..b58fc7353b5fa 100644
--- a/tests/phpunit/tests/media.php
+++ b/tests/phpunit/tests/media.php
@@ -1833,6 +1833,31 @@ public function test_wp_calculate_image_srcset_with_absolute_path_in_meta() {
 		}
 	}
 
+	/**
+	 * @ticket 61690
+	 * @requires function imagejpeg
+	 */
+	public function test_wp_calculate_image_srcset_with_relative_content_url() {
+		$_SERVER['HTTPS'] = 'on';
+
+		add_filter(
+			'upload_dir',
+			static function ( $upload_dir ) {
+				$upload_dir['baseurl'] = '/wp-content/uploads';
+				return $upload_dir;
+			}
+		);
+
+		$image_url  = wp_get_attachment_image_url( self::$large_id, 'medium' );
+		$image_meta = wp_get_attachment_metadata( self::$large_id );
+
+		$size_array = array( 300, 225 );
+
+		$srcset = wp_calculate_image_srcset( $size_array, $image_url, $image_meta );
+
+		$this->assertStringStartsWith( '/wp-content/uploads', $srcset );
+	}
+
 	/**
 	 * @ticket 33641
 	 */