diff --git a/src/emu/bus/ql/sandy_superdisk.c b/src/emu/bus/ql/sandy_superdisk.c
index d1a1b04d1d2..4661572c3af 100644
--- a/src/emu/bus/ql/sandy_superdisk.c
+++ b/src/emu/bus/ql/sandy_superdisk.c
@@ -250,7 +250,7 @@ void sandy_super_disk_t::write(address_space &space, offs_t offset, UINT8 data)
 				if (floppy)
 				{
 					floppy->ss_w(BIT(data, 0));
-					floppy->mon_w(BIT(data, 3));
+					floppy->mon_w(!BIT(data, 3));
 				}
 
 				m_fdc->dden_w(BIT(data, 4));
diff --git a/src/emu/bus/ql/sandy_superqboard.c b/src/emu/bus/ql/sandy_superqboard.c
index 9d0563a9bbc..dc1176a330f 100644
--- a/src/emu/bus/ql/sandy_superqboard.c
+++ b/src/emu/bus/ql/sandy_superqboard.c
@@ -318,7 +318,7 @@ void sandy_superqboard_t::write(address_space &space, offs_t offset, UINT8 data)
 				if (floppy)
 				{
 					floppy->ss_w(BIT(data, 0));
-					floppy->mon_w(BIT(data, 3));
+					floppy->mon_w(!BIT(data, 3));
 				}
 
 				m_fdc->dden_w(BIT(data, 4));
diff --git a/src/emu/bus/ql/trumpcard.c b/src/emu/bus/ql/trumpcard.c
index 4f75e36e040..01f56d81c76 100644
--- a/src/emu/bus/ql/trumpcard.c
+++ b/src/emu/bus/ql/trumpcard.c
@@ -282,7 +282,7 @@ void ql_trump_card_t::write(address_space &space, offs_t offset, UINT8 data)
 		if (floppy)
 		{
 			floppy->ss_w(BIT(data, 3));
-			floppy->mon_w(BIT(data, 2));
+			floppy->mon_w(!BIT(data, 2));
 		}
 	}