diff --git a/buspirate_spi.c b/buspirate_spi.c
index db8b310..fad309f 100644
--- a/buspirate_spi.c
+++ b/buspirate_spi.c
@@ -543,6 +543,10 @@
 
 	/* Set SPI config: output type, idle, clock edge, sample */
 	bp_commbuf[0] = 0x80 | 0xa;
+	if (pullup == 1) {
+		bp_commbuf[0] &= ~(1 << 3);
+		msg_pdbg("Pull-ups enabled, so using HiZ pin output! (Open-Drain mode)\n");
+	}
 	ret = buspirate_sendrecv(bp_commbuf, 1, 1);
 	if (ret)
 		return 1;