diff --git a/src/mame/drivers/thayers.cpp b/src/mame/drivers/thayers.cpp
index 9df9043f85e..3b978e2d41f 100644
--- a/src/mame/drivers/thayers.cpp
+++ b/src/mame/drivers/thayers.cpp
@@ -777,7 +777,7 @@ static MACHINE_CONFIG_START( thayers, thayers_state )
 	MCFG_CPU_IO_MAP(thayers_io_map)
 
 	MCFG_CPU_ADD("mcu", COP421, XTAL_4MHz/2) // COP421L-PCA/N
-	MCFG_COP400_CONFIG( COP400_CKI_DIVISOR_4, COP400_CKO_OSCILLATOR_OUTPUT, false )
+	MCFG_COP400_CONFIG( COP400_CKI_DIVISOR_16, COP400_CKO_OSCILLATOR_OUTPUT, false )
 	MCFG_COP400_READ_L_CB(READ8(thayers_state, cop_l_r))
 	MCFG_COP400_WRITE_L_CB(WRITE8(thayers_state, cop_l_w))
 	MCFG_COP400_READ_G_CB(READ8(thayers_state, cop_g_r))