diff --git a/protocols/upnp/src/behaviour.rs b/protocols/upnp/src/behaviour.rs
index adfa60f6e94..035561689f6 100644
--- a/protocols/upnp/src/behaviour.rs
+++ b/protocols/upnp/src/behaviour.rs
@@ -23,6 +23,7 @@
 use std::{
     borrow::Borrow,
     collections::HashMap,
+    error::Error,
     hash::{Hash, Hasher},
     net::{Ipv4Addr, SocketAddrV4},
     pin::Pin,
@@ -90,11 +91,11 @@ enum Event {
     /// Port was successfully mapped.
     Mapped(Mapping),
     /// There was a failure mapping port.
-    MapFailure(Mapping, String),
+    MapFailure(Mapping, Box<dyn Error + Send + Sync + 'static>),
     /// Port was successfully removed.
     Removed(Mapping),
     /// There was a failure removing the mapping port.
-    RemovalFailure(Mapping, String),
+    RemovalFailure(Mapping, Box<dyn Error + Send + Sync + 'static>),
 }
 
 /// Mapping of a Protocol and Port on the gateway.
diff --git a/protocols/upnp/src/gateway.rs b/protocols/upnp/src/gateway.rs
index 4ad8cf665d9..3d8155e123b 100644
--- a/protocols/upnp/src/gateway.rs
+++ b/protocols/upnp/src/gateway.rs
@@ -64,10 +64,14 @@ pub trait Gateway: Sized + Send + Sync {
         protocol: Protocol,
         addr: SocketAddrV4,
         duration: Duration,
-    ) -> Result<(), String>;
+    ) -> Result<(), Box<dyn Error + Send + Sync + 'static>>;
 
     /// Remove port mapping on the gateway.
-    async fn remove_port(_: Arc<Self>, protocol: Protocol, port: u16) -> Result<(), String>;
+    async fn remove_port(
+        _: Arc<Self>,
+        protocol: Protocol,
+        port: u16,
+    ) -> Result<(), Box<dyn Error + Send + Sync + 'static>>;
 
     // /// Spawn a future on the executor.
     fn spawn<F>(f: F)
diff --git a/protocols/upnp/src/gateway/async_std.rs b/protocols/upnp/src/gateway/async_std.rs
index 351c196a0fe..7b199c67579 100644
--- a/protocols/upnp/src/gateway/async_std.rs
+++ b/protocols/upnp/src/gateway/async_std.rs
@@ -53,7 +53,7 @@ impl super::Gateway for Gateway {
         protocol: Protocol,
         addr: SocketAddrV4,
         duration: Duration,
-    ) -> Result<(), String> {
+    ) -> Result<(), Box<dyn Error + Send + Sync + 'static>> {
         let protocol = match protocol {
             Protocol::Tcp => PortMappingProtocol::TCP,
             Protocol::Udp => PortMappingProtocol::UDP,
@@ -67,10 +67,14 @@ impl super::Gateway for Gateway {
                 "rust-libp2p mapping",
             )
             .await
-            .map_err(|err| err.to_string())
+            .map_err(|err| err.into())
     }
 
-    async fn remove_port(gateway: Arc<Self>, protocol: Protocol, port: u16) -> Result<(), String> {
+    async fn remove_port(
+        gateway: Arc<Self>,
+        protocol: Protocol,
+        port: u16,
+    ) -> Result<(), Box<dyn Error + Send + Sync + 'static>> {
         let protocol = match protocol {
             Protocol::Tcp => PortMappingProtocol::TCP,
             Protocol::Udp => PortMappingProtocol::UDP,
@@ -78,7 +82,7 @@ impl super::Gateway for Gateway {
         gateway
             .remove_port(protocol, port)
             .await
-            .map_err(|err| err.to_string())
+            .map_err(|err| err.into())
     }
     fn spawn<F>(f: F)
     where
diff --git a/protocols/upnp/src/gateway/tokio.rs b/protocols/upnp/src/gateway/tokio.rs
index 2c035566b03..febc691c85d 100644
--- a/protocols/upnp/src/gateway/tokio.rs
+++ b/protocols/upnp/src/gateway/tokio.rs
@@ -53,7 +53,7 @@ impl super::Gateway for Gateway {
         protocol: Protocol,
         addr: SocketAddrV4,
         duration: Duration,
-    ) -> Result<(), String> {
+    ) -> Result<(), Box<dyn Error + Send + Sync + 'static>> {
         let protocol = match protocol {
             Protocol::Tcp => PortMappingProtocol::TCP,
             Protocol::Udp => PortMappingProtocol::UDP,
@@ -67,10 +67,14 @@ impl super::Gateway for Gateway {
                 "rust-libp2p mapping",
             )
             .await
-            .map_err(|err| err.to_string())
+            .map_err(|err| err.into())
     }
 
-    async fn remove_port(gateway: Arc<Self>, protocol: Protocol, port: u16) -> Result<(), String> {
+    async fn remove_port(
+        gateway: Arc<Self>,
+        protocol: Protocol,
+        port: u16,
+    ) -> Result<(), Box<dyn Error + Send + Sync + 'static>> {
         let protocol = match protocol {
             Protocol::Tcp => PortMappingProtocol::TCP,
             Protocol::Udp => PortMappingProtocol::UDP,
@@ -78,7 +82,7 @@ impl super::Gateway for Gateway {
         gateway
             .remove_port(protocol, port)
             .await
-            .map_err(|err| err.to_string())
+            .map_err(|err| err.into())
     }
 
     fn spawn<F>(f: F)