diff --git a/Source/HBIOS/ch376ufi.asm b/Source/HBIOS/ch376ufi.asm
index e0eefbd6..5c005930 100644
--- a/Source/HBIOS/ch376ufi.asm
+++ b/Source/HBIOS/ch376ufi.asm
@@ -156,6 +156,7 @@ CH_UFI_READ:
 	POP	HL
 	LD	BC, 512
 	ADD	HL, BC
+	OR	A
 	RET
 ;
 ; ### Function 0x14 -- Disk Write (DIOWRITE)
@@ -194,6 +195,7 @@ CH_UFI_WRITE:
 	POP	HL
 	LD	BC, 512
 	ADD	HL, BC
+	OR	A
 	RET
 
 CH_UFI_VERIFY: