diff --git a/hw/usb/dev-smartcard-reader.c b/hw/usb/dev-smartcard-reader.c
index 757b8b3f5a..49cb1829b5 100644
--- a/hw/usb/dev-smartcard-reader.c
+++ b/hw/usb/dev-smartcard-reader.c
@@ -813,7 +813,10 @@ static void ccid_write_data_block(USBCCIDState *s, uint8_t slot, uint8_t seq,
     if (p->b.bError) {
         DPRINTF(s, D_VERBOSE, "error %d\n", p->b.bError);
     }
-    memcpy(p->abData, data, len);
+    if (len) {
+        g_assert_nonnull(data);
+        memcpy(p->abData, data, len);
+    }
     ccid_reset_error_status(s);
     usb_wakeup(s->bulk, 0);
 }