diff --git a/src/mame/machine/tecmosys.c b/src/mame/machine/tecmosys.c
index 093af2b8765..6071173f45f 100644
--- a/src/mame/machine/tecmosys.c
+++ b/src/mame/machine/tecmosys.c
@@ -206,16 +206,13 @@ WRITE16_MEMBER(tecmosys_state::tecmosys_prot_data_w)
 			break;
 
 		case DS_SEND_CHKSUMS:
-			if( m_device_read_ptr >= 5 )
+			if( m_device_read_ptr >= 4 )
 			{
 				m_device_status = DS_DONE;
 				m_device_value = 0;
 			}
 			else
-			{
-				assert(m_device_read_ptr >= 0 && m_device_read_ptr < ARRAY_LENGTH(m_device_data->checksums));
 				m_device_value = data == m_device_data->checksums[m_device_read_ptr] ? m_device_data->checksums[m_device_read_ptr++] : 0xff;
-			}
 			break;
 
 		case DS_DONE: