diff --git a/actix-web-codegen/src/route.rs b/actix-web-codegen/src/route.rs
index a4472efd2..cb1ba1ef6 100644
--- a/actix-web-codegen/src/route.rs
+++ b/actix-web-codegen/src/route.rs
@@ -302,13 +302,13 @@ impl ToTokens for Route {
             if methods.len() > 1 {
                 quote! {
                     .guard(
-                        actix_web::guard::Any(actix_web::guard::#first())
-                            #(.or(actix_web::guard::#others()))*
+                        ::actix_web::guard::Any(::actix_web::guard::#first())
+                            #(.or(::actix_web::guard::#others()))*
                     )
                 }
             } else {
                 quote! {
-                    .guard(actix_web::guard::#first())
+                    .guard(::actix_web::guard::#first())
                 }
             }
         };
@@ -318,17 +318,17 @@ impl ToTokens for Route {
             #[allow(non_camel_case_types, missing_docs)]
             pub struct #name;
 
-            impl actix_web::dev::HttpServiceFactory for #name {
+            impl ::actix_web::dev::HttpServiceFactory for #name {
                 fn register(self, __config: &mut actix_web::dev::AppService) {
                     #ast
-                    let __resource = actix_web::Resource::new(#path)
+                    let __resource = ::actix_web::Resource::new(#path)
                         .name(#resource_name)
                         #method_guards
-                        #(.guard(actix_web::guard::fn_guard(#guards)))*
+                        #(.guard(::actix_web::guard::fn_guard(#guards)))*
                         #(.wrap(#wrappers))*
                         .#resource_type(#name);
 
-                    actix_web::dev::HttpServiceFactory::register(__resource, __config)
+                    ::actix_web::dev::HttpServiceFactory::register(__resource, __config)
                 }
             }
         };
diff --git a/src/request.rs b/src/request.rs
index d721f2ac7..63db56fd3 100644
--- a/src/request.rs
+++ b/src/request.rs
@@ -138,6 +138,10 @@ impl HttpRequest {
         &self.inner.path
     }
 
+    /// Returns a mutable reference to the URL parameters container.
+    ///
+    /// # Panics
+    /// Panics if this `HttpRequest` has been cloned.
     #[inline]
     pub(crate) fn match_info_mut(&mut self) -> &mut Path<Url> {
         &mut Rc::get_mut(&mut self.inner).unwrap().path
diff --git a/src/service.rs b/src/service.rs
index 162c90ec8..81424a654 100644
--- a/src/service.rs
+++ b/src/service.rs
@@ -97,6 +97,11 @@ impl ServiceRequest {
 
     /// Construct request from parts.
     pub fn from_parts(req: HttpRequest, payload: Payload) -> Self {
+        #[cfg(debug_assertions)]
+        if Rc::strong_count(&req.inner) > 1 {
+            log::warn!("Cloning an `HttpRequest` might cause panics.");
+        }
+
         Self { req, payload }
     }
 
@@ -663,7 +668,7 @@ service_tuple! { A B C D E F G H I J K L }
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::test::{init_service, TestRequest};
+    use crate::test::{self, init_service, TestRequest};
     use crate::{guard, http, web, App, HttpResponse};
     use actix_service::Service;
     use actix_utils::future::ok;
@@ -810,4 +815,29 @@ mod tests {
         let resp = srv.call(req).await.unwrap();
         assert_eq!(resp.status(), http::StatusCode::OK);
     }
+
+    #[actix_rt::test]
+    #[should_panic(expected = "called `Option::unwrap()` on a `None` value")]
+    async fn cloning_request_panics() {
+        async fn index(_name: web::Path<(String,)>) -> &'static str {
+            ""
+        }
+
+        let app = test::init_service(
+            App::new()
+                .wrap_fn(|req, svc| {
+                    let (req, pl) = req.into_parts();
+                    let _req2 = req.clone();
+                    let req = ServiceRequest::from_parts(req, pl);
+                    svc.call(req)
+                })
+                .service(
+                    web::resource("/resource1/{name}/index.html").route(web::get().to(index)),
+                ),
+        )
+        .await;
+
+        let req = test::TestRequest::default().to_request();
+        let _res = test::call_service(&app, req).await;
+    }
 }