diff --git a/pdu/submit.go b/pdu/submit.go
index 3c1957f..033702d 100644
--- a/pdu/submit.go
+++ b/pdu/submit.go
@@ -135,7 +135,7 @@ func (p *SUBMIT_SM) Size() int {
 }
 func (p *SUBMIT_SM) UpdateSize() {
 	p.header.command_length = uint32(p.Size())
-	p.sm_length = byte(len(p.short_message))
+	p.sm_length = byte(p.GetEncoder().EncodesInto(&p.short_message))
 }
 func (p *SUBMIT_SM) GetEncoder() encoding.Coder {
 	switch p.data_coding {
diff --git a/pdu/submit_test.go b/pdu/submit_test.go
index 48a2661..6949051 100644
--- a/pdu/submit_test.go
+++ b/pdu/submit_test.go
@@ -45,25 +45,43 @@ func TestEncodeFunctionCorrectlyEncodesAllFields(t *testing.T) {
 	}
 }
 
-// func TestRealScenario(t *testing.T) {
-//
-// 	p.header.command_length = uint32(p.Size())
-// 	p.sm_length = byte(len(p.short_message))
-// 	buf := make([]byte, p.Size())
-// 	err := p.EncodeInto(&buf)
-// 	if err != nil {
-// 		t.Errorf("Expected no error, got %v", err)
-// 	}
-// 	if len(buf) != len(expected) {
-// 		t.Errorf("Expected byte slice of length %d, got %d", len(expected), len(buf))
-// 	}
-// 	for i, v := range buf {
-// 		if v != expected[i] {
-// 			t.Errorf("Expected byte slice with values %v, got %v", expected, buf)
-// 			break
-// 		}
-// 	}
-// }
+func TestEncodeFunctionCorrectlyEncodesAllFieldsGSM7Message(t *testing.T) {
+	p := &SUBMIT_SM{
+		header: &PDU_HEADER{
+			command_length:  0,
+			command_id:      4,
+			command_status:  0,
+			sequence_number: 378019,
+		},
+		service_type:           "OMV4",
+		source_addr_ton:        3,
+		source_addr_npi:        1,
+		source_addr:            "80362",
+		dest_addr_ton:          1,
+		dest_addr_npi:          1,
+		destination_addr:       "812345001000",
+		esm_class:              0,
+		protocol_id:            0,
+		priority_flag:          0,
+		schedule_delivery_time: "",
+		validity_period:        "180105120000004+",
+		registered_delivery:    1,
+		data_coding:            0, // The example uses 0 and claims to use GSM but the message is encoded as ASCII...
+		sm_default_msg_id:      0,
+		short_message:          "Reply Yes to opt in or No to opt out.",
+	}
+	p.UpdateSize()
+	buf := ByteBufferPool.Get(p.Size())
+	err := p.Encode(buf)
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+
+	expected := []byte{0, 0, 0, 103, 0, 0, 0, 4, 0, 0, 0, 0, 0, 5, 196, 163, 79, 77, 86, 52, 0, 3, 1, 56, 48, 51, 54, 50, 0, 1, 1, 56, 49, 50, 51, 52, 53, 48, 48, 49, 48, 48, 48, 0, 0, 0, 0, 0, 49, 56, 48, 49, 48, 53, 49, 50, 48, 48, 48, 48, 48, 48, 52, 43, 0, 1, 0, 0, 0, 33, 210, 50, 156, 157, 7, 101, 203, 115, 16, 253, 13, 122, 195, 233, 160, 180, 27, 244, 150, 131, 156, 111, 16, 253, 13, 122, 195, 233, 160, 119, 157, 238, 2}
+	if !bytes.Equal(buf.Bytes(), expected) {
+		t.Fatalf("expected %v, got %v", expected, buf.Bytes())
+	}
+}
 
 // region decode