diff --git a/hw/sd/sd.c b/hw/sd/sd.c
index d06e670024..18bb2f9fd8 100644
--- a/hw/sd/sd.c
+++ b/hw/sd/sd.c
@@ -601,6 +601,14 @@ static void sd_response_r7_make(SDState *sd, uint8_t *response)
     stl_be_p(response, sd->vhs);
 }
 
+static uint32_t sd_blk_len(SDState *sd)
+{
+    if (FIELD_EX32(sd->ocr, OCR, CARD_CAPACITY)) {
+        return 1 << HWBLOCK_SHIFT;
+    }
+    return sd->blk_len;
+}
+
 static uint64_t sd_req_get_address(SDState *sd, SDRequest req)
 {
     uint64_t addr;
@@ -2074,7 +2082,7 @@ uint8_t sd_read_byte(SDState *sd)
     if (sd->card_status & (ADDRESS_ERROR | WP_VIOLATION))
         return 0x00;
 
-    io_len = (sd->ocr & (1 << 30)) ? 512 : sd->blk_len;
+    io_len = sd_blk_len(sd);
 
     trace_sdcard_read_data(sd->proto->name,
                            sd->last_cmd_name,