diff --git a/docs/src/main/asciidoc/spring-cloud-gateway.adoc b/docs/src/main/asciidoc/spring-cloud-gateway.adoc
index 7dd3e8e8..8bafebe2 100644
--- a/docs/src/main/asciidoc/spring-cloud-gateway.adoc
+++ b/docs/src/main/asciidoc/spring-cloud-gateway.adoc
@@ -2495,7 +2495,7 @@ public class PreGatewayFilterFactory extends AbstractGatewayFilterFactory<PreGat
 			//request before calling chain.filter
 			ServerHttpRequest.Builder builder = exchange.getRequest().mutate();
 			//use builder to manipulate the request
-			return chain.filter(exchange.mutate().request(request).build());
+			return chain.filter(exchange.mutate().request(builder.build()).build());
 		};
 	}
 
@@ -2534,6 +2534,19 @@ public class PostGatewayFilterFactory extends AbstractGatewayFilterFactory<PostG
 ----
 ====
 
+==== Naming Custom Filters And References In Configuration
+
+Custom filters class names should end in `GatewayFilterFactory`.
+
+For example, to reference a filter named `Something` in configuration files, the filter
+must be in a class named `SomethingGatewayFilterFactory`.
+
+WARNING: It is possible to create a gateway filter named without the
+`GatewayFilterFactory` suffix, such as `class AnotherThing`. This filter could be
+referenced as `AnotherThing` in configuration files. This is **not** a supported naming
+convention and this syntax may be removed in future releases. Please update the filter
+name to be compliant.
+
 === Writing Custom Global Filters
 
 To write a custom global filter, you must implement `GlobalFilter` interface.