diff --git a/src/hdd_esdi.c b/src/hdd_esdi.c
index 1b32b1b..8bbc41e 100644
--- a/src/hdd_esdi.c
+++ b/src/hdd_esdi.c
@@ -437,6 +437,7 @@ static void esdi_callback(void *p)
                                         if (esdi->rba >= hdd_file->sectors)
                                                 fatal("Read past end of drive\n");
                                         hdd_read_sectors(hdd_file, esdi->rba, 1, esdi->data);
+                                        readflash_set(READFLASH_HDC, esdi->cmd_dev == ATTN_DEVICE_0 ? 0 : 1);
                                 }
 //                                pclog("Read sector %i %i %08x\n", esdi->sector_pos, esdi->data_pos, esdi->rba*512);
                                 while (esdi->data_pos < 256)
diff --git a/src/ibm.h b/src/ibm.h
index 2ad1aa3..a314370 100644
--- a/src/ibm.h
+++ b/src/ibm.h
@@ -5,9 +5,9 @@
 
 #define READFLASH_FDC 0
 #define READFLASH_HDC 4
-#define readflash_set(offset, drive) readflash |= 1<<(offset+drive)
-#define readflash_clear(offset, drive) readflash &= ~(1<<(offset+drive))
-#define readflash_get(offset, drive) ((readflash&(1<<(offset+drive))) != 0)
+#define readflash_set(offset, drive) readflash |= 1<<((offset)+(drive))
+#define readflash_clear(offset, drive) readflash &= ~(1<<((offset)+(drive)))
+#define readflash_get(offset, drive) ((readflash&(1<<((offset)+(drive)))) != 0)
 
 /*Memory*/
 uint8_t *ram;