diff --git a/hw/usb/bus.c b/hw/usb/bus.c
index 796769f..bfab280 100644
--- a/hw/usb/bus.c
+++ b/hw/usb/bus.c
@@ -260,13 +260,14 @@
     }
 
     if (dev->pcap_filename) {
-        int fd = qemu_open_old(dev->pcap_filename, O_CREAT | O_WRONLY | O_TRUNC, 0666);
+        int fd = qemu_open_old(dev->pcap_filename,
+                               O_CREAT | O_WRONLY | O_TRUNC | O_BINARY, 0666);
         if (fd < 0) {
             error_setg(errp, "open %s failed", dev->pcap_filename);
             usb_qdev_unrealize(qdev);
             return;
         }
-        dev->pcap = fdopen(fd, "w");
+        dev->pcap = fdopen(fd, "wb");
         usb_pcap_init(dev->pcap);
     }
 }