diff --git a/src/mame/drivers/trs80m3.cpp b/src/mame/drivers/trs80m3.cpp
index 1cd18228c0f..d40be698f0b 100644
--- a/src/mame/drivers/trs80m3.cpp
+++ b/src/mame/drivers/trs80m3.cpp
@@ -531,6 +531,6 @@ void trs80m3_state::init_trs80m4p()
 
 //    YEAR  NAME         PARENT    COMPAT    MACHINE   INPUT     CLASS          INIT             COMPANY               FULLNAME                FLAGS
 COMP( 1980, trs80m3,     0,        trs80l2,  model3,   trs80m3,  trs80m3_state, init_trs80m3,  "Tandy Radio Shack", "TRS-80 Model III",        MACHINE_SUPPORTS_SAVE )
-COMP( 1980, trs80m4,     trs80m3,  0,        model4,   trs80m3,  trs80m3_state, init_trs80m4,  "Tandy Radio Shack", "TRS-80 Model 4",          MACHINE_SUPPORTS_SAVE )
+COMP( 1980, trs80m4,     trs80m3,  0,        model4,   trs80m3,  trs80m3_state, init_trs80m4,  "Tandy Radio Shack", "TRS-80 Model 4",          MACHINE_NOT_WORKING | MACHINE_SUPPORTS_SAVE )
 COMP( 1983, trs80m4p,    trs80m3,  0,        model4p,  trs80m4p, trs80m3_state, init_trs80m4p, "Tandy Radio Shack", "TRS-80 Model 4P",         MACHINE_NOT_WORKING | MACHINE_SUPPORTS_SAVE)
 COMP( 1982, cp500,       trs80m3,  0,        cp500,    trs80m3,  trs80m3_state, init_trs80m3,  "Prológica",         "CP-500 (PVIII REV.3)",    MACHINE_SUPPORTS_SAVE )