diff --git a/src/mess/drivers/thomson.c b/src/mess/drivers/thomson.c
index 80cdf4533e1..fa07edb41b9 100644
--- a/src/mess/drivers/thomson.c
+++ b/src/mess/drivers/thomson.c
@@ -564,15 +564,16 @@ static INPUT_PORTS_START ( t9000 )
 	PORT_INCLUDE ( to7 )
 INPUT_PORTS_END
 
-static WRITE_LINE_DEVICE_HANDLER(thomson_index_callback)
+WRITE_LINE_MEMBER( thomson_state::fdc_index_w )
 {
-	device->machine().driver_data<thomson_state>()->thomson_index_callback(device, state);
+  device_t *device = machine().device<wd2793_device>("wd2793");
+  thomson_index_callback(device, state);
 }
 
 
 static const floppy_interface thomson_floppy_interface =
 {
-	DEVCB_LINE(thomson_index_callback),
+	DEVCB_DRIVER_LINE_MEMBER(thomson_state, fdc_index_w),
 	DEVCB_NULL,
 	DEVCB_NULL,
 	DEVCB_NULL,
diff --git a/src/mess/includes/thomson.h b/src/mess/includes/thomson.h
index 4f568a2a9fb..620ea5b49c4 100644
--- a/src/mess/includes/thomson.h
+++ b/src/mess/includes/thomson.h
@@ -296,6 +296,7 @@ public:
 	DECLARE_WRITE8_MEMBER( to7_floppy_w );
 	DECLARE_READ8_MEMBER( to9_floppy_r );
 	DECLARE_WRITE8_MEMBER( to9_floppy_w );
+	WRITE_LINE_MEMBER( fdc_index_w );
 	void thomson_index_callback(device_t *device, int state);
 	DECLARE_PALETTE_INIT(thom);