diff --git a/miner_runtime.go b/miner_runtime.go
index f14c945..6090cf5 100644
--- a/miner_runtime.go
+++ b/miner_runtime.go
@@ -294,6 +294,11 @@ func (m *Miner) handleSubmit(request minerRequest) {
 		return
 	}
 
+	submitAlgo := ""
+	if m.algoExtension && m.extAlgo {
+		submitAlgo = params.Algo
+	}
+
 	m.Touch()
 	if m.events != nil {
 		m.events.Dispatch(Event{
@@ -302,7 +307,7 @@ func (m *Miner) handleSubmit(request minerRequest) {
 			JobID:     params.JobID,
 			Nonce:     params.Nonce,
 			Result:    params.Result,
-			Algo:      params.Algo,
+			Algo:      submitAlgo,
 			RequestID: request.ID,
 		})
 		return
@@ -314,7 +319,7 @@ func (m *Miner) handleSubmit(request minerRequest) {
 			JobID:     params.JobID,
 			Nonce:     params.Nonce,
 			Result:    params.Result,
-			Algo:      params.Algo,
+			Algo:      submitAlgo,
 			RequestID: request.ID,
 		})
 	}
diff --git a/miner_runtime_test.go b/miner_runtime_test.go
index b6d48b5..c30289d 100644
--- a/miner_runtime_test.go
+++ b/miner_runtime_test.go
@@ -240,6 +240,8 @@ func TestMiner_Submit_Good(t *testing.T) {
 
 	miner := NewMiner(serverConn, 3333, nil)
 	miner.events = NewEventBus()
+	miner.algoExtension = true
+	miner.extAlgo = true
 	miner.SetRPCID("session")
 	miner.SetState(MinerStateReady)
 
@@ -292,3 +294,47 @@ func TestMiner_Submit_Good(t *testing.T) {
 		t.Fatalf("unexpected submit response: %#v", response)
 	}
 }
+
+func TestMiner_Submit_AlgoExtension_Bad(t *testing.T) {
+	serverConn, clientConn := net.Pipe()
+	defer clientConn.Close()
+
+	miner := NewMiner(serverConn, 3333, nil)
+	miner.events = NewEventBus()
+	miner.SetRPCID("session")
+	miner.SetState(MinerStateReady)
+
+	submitSeen := make(chan Event, 1)
+	miner.events.Subscribe(EventSubmit, func(event Event) {
+		submitSeen <- event
+		miner.Success(event.RequestID, "OK")
+	})
+
+	miner.Start()
+	defer miner.Close()
+
+	encoder := json.NewEncoder(clientConn)
+	if err := encoder.Encode(map[string]interface{}{
+		"id":      7,
+		"jsonrpc": "2.0",
+		"method":  "submit",
+		"params": map[string]interface{}{
+			"id":     "session",
+			"job_id": "job-1",
+			"nonce":  "deadbeef",
+			"result": "abc",
+			"algo":   "cn/r",
+		},
+	}); err != nil {
+		t.Fatal(err)
+	}
+
+	select {
+	case event := <-submitSeen:
+		if event.Algo != "" {
+			t.Fatalf("expected algo to be suppressed when extension is disabled, got %+v", event)
+		}
+	case <-time.After(time.Second):
+		t.Fatal("expected submit event to be dispatched")
+	}
+}