diff --git a/Cargo.lock b/Cargo.lock
index 63a9e53c335..2aa715a660c 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -799,6 +799,7 @@ dependencies = [
  "c8y_auth_proxy",
  "c8y_http_proxy",
  "camino",
+ "capture-logger",
  "clock",
  "json-writer",
  "logged_command",
@@ -837,6 +838,15 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "capture-logger"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "605a59c5054ce9e87cd329251bcc4c04579d5edbd206b1e4c45fbfe24b13ff82"
+dependencies = [
+ "log",
+]
+
 [[package]]
 name = "cc"
 version = "1.0.83"
diff --git a/Cargo.toml b/Cargo.toml
index 823d9a9ae4d..8a9b7b81299 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -60,6 +60,7 @@ certificate = { path = "crates/common/certificate" }
 clap = { version = "4.4", features = ["cargo", "derive"] }
 clock = { path = "crates/common/clock" }
 collectd_ext = { path = "crates/extensions/collectd_ext" }
+capture-logger = "0.1"
 csv = "1.1"
 darling = "0.20"
 doku = "0.21"
diff --git a/crates/core/tedge_api/src/entity_store.rs b/crates/core/tedge_api/src/entity_store.rs
index 402d7418682..edf80ad2dac 100644
--- a/crates/core/tedge_api/src/entity_store.rs
+++ b/crates/core/tedge_api/src/entity_store.rs
@@ -586,7 +586,7 @@ pub enum Error {
     #[error("The specified entity {0} does not exist in the store")]
     UnknownEntity(String),
 
-    #[error("The specified topic id {0} does not match the default topic scheme: 'device/<device-id>/service/<service-id>'")]
+    #[error("Auto registration of the entity with topic id {0} failed as it does not match the default topic scheme: 'device/<device-id>/service/<service-id>'. Try explicit registration instead.")]
     NonDefaultTopicScheme(EntityTopicId),
 
     #[error(transparent)]
diff --git a/crates/extensions/c8y_mapper_ext/Cargo.toml b/crates/extensions/c8y_mapper_ext/Cargo.toml
index 51c0860deb6..824e5faa876 100644
--- a/crates/extensions/c8y_mapper_ext/Cargo.toml
+++ b/crates/extensions/c8y_mapper_ext/Cargo.toml
@@ -49,9 +49,11 @@ tracing = { workspace = true }
 [dev-dependencies]
 assert-json-diff = { workspace = true }
 assert_matches = { workspace = true }
+capture-logger = { workspace = true }
 proptest = { workspace = true }
 rand = { workspace = true }
 tedge_actors = { workspace = true, features = ["test-helpers"] }
 tedge_mqtt_ext = { workspace = true, features = ["test-helpers"] }
 tedge_test_utils = { workspace = true }
 test-case = { workspace = true }
+
diff --git a/crates/extensions/c8y_mapper_ext/src/converter.rs b/crates/extensions/c8y_mapper_ext/src/converter.rs
index c363680285e..0c87025007a 100644
--- a/crates/extensions/c8y_mapper_ext/src/converter.rs
+++ b/crates/extensions/c8y_mapper_ext/src/converter.rs
@@ -967,7 +967,20 @@ impl CumulocityConverter {
                 // if device is unregistered register using auto-registration
                 if self.entity_store.get(&source).is_none() {
                     let auto_registration_messages =
-                        self.entity_store.auto_register_entity(&source)?;
+                        match self.entity_store.auto_register_entity(&source) {
+                            Ok(auto_registration_messages) => auto_registration_messages,
+                            Err(e) => match e {
+                                Error::NonDefaultTopicScheme(eid) => {
+                                    debug!("{}", Error::NonDefaultTopicScheme(eid.clone()));
+                                    return Ok(vec![self.new_error_message(
+                                        ConversionError::FromEntityStoreError(
+                                            entity_store::Error::NonDefaultTopicScheme(eid),
+                                        ),
+                                    )]);
+                                }
+                                e => return Err(e.into()),
+                            },
+                        };
                     for auto_registration_message in &auto_registration_messages {
                         registration_messages.append(
                             &mut self.register_and_convert_entity(auto_registration_message)?,
@@ -3020,6 +3033,28 @@ pub(crate) mod tests {
         }
     }
 
+    #[tokio::test]
+    async fn try_auto_registration_on_custom_topic() -> Result<(), anyhow::Error> {
+        use capture_logger::begin_capture;
+        use capture_logger::pop_captured;
+        let tmp_dir = TempTedgeDir::new();
+        let (mut converter, _http_proxy) = create_c8y_converter(&tmp_dir).await;
+
+        let alarm_topic = "te/custom/child2///m/";
+        let alarm_payload = json!({ "text": "" }).to_string();
+        let alarm_message = Message::new(&Topic::new_unchecked(alarm_topic), alarm_payload);
+        begin_capture();
+        let res = converter.try_convert(&alarm_message).await.unwrap();
+        let expected_err_msg = Message::new(&Topic::new_unchecked("te/errors"), "Auto registration of the entity with topic id custom/child2// failed as it does not match the default topic scheme: 'device/<device-id>/service/<service-id>'. Try explicit registration instead.");
+        assert_eq!(res[0], expected_err_msg);
+        let expected_log = "Auto registration of the entity with topic id custom/child2// failed as it does not match the default topic scheme: 'device/<device-id>/service/<service-id>'. Try explicit registration instead.";
+        // skip other log messages
+        pop_captured().unwrap().message();
+        pop_captured().unwrap().message();
+        assert_eq!(pop_captured().unwrap().message(), expected_log);
+        Ok(())
+    }
+
     pub(crate) async fn create_c8y_converter(
         tmp_dir: &TempTedgeDir,
     ) -> (