diff --git a/src/devices/bus/a2bus/byte8251.h b/src/devices/bus/a2bus/byte8251.h
index 450f221f8f4..557e714cda1 100644
--- a/src/devices/bus/a2bus/byte8251.h
+++ b/src/devices/bus/a2bus/byte8251.h
@@ -26,6 +26,7 @@ protected:
 	// device_a2bus_card_interface overrides
 	virtual u8 read_c0nx(u8 offset) override;
 	virtual void write_c0nx(u8 offset, u8 data) override;
+	virtual bool take_c800() override { return false; }
 
 private:
 	// object finders
diff --git a/src/devices/bus/a2bus/ccs7710.h b/src/devices/bus/a2bus/ccs7710.h
index 3c65b9b783f..db2a7616891 100644
--- a/src/devices/bus/a2bus/ccs7710.h
+++ b/src/devices/bus/a2bus/ccs7710.h
@@ -32,6 +32,7 @@ protected:
 	virtual u8 read_c0nx(u8 offset) override;
 	virtual void write_c0nx(u8 offset, u8 data) override;
 	virtual u8 read_cnxx(u8 offset) override;
+	virtual bool take_c800() override { return false; }
 
 private:
 	// miscellaneous handlers