diff --git a/sys/bus/u4b/serial/uchcom.c b/sys/bus/u4b/serial/uchcom.c
--- a/sys/bus/u4b/serial/uchcom.c
+++ b/sys/bus/u4b/serial/uchcom.c
@@ -414,7 +414,7 @@
 uchcom_read_reg(struct uchcom_softc *sc,
     uint8_t reg1, uint8_t *rval1, uint8_t reg2, uint8_t *rval2)
 {
-	uint8_t buf[UCHCOM_INPUT_BUF_SIZE];
+	uint8_t buf[UCHCOM_INPUT_BUF_SIZE] = {0};
 
 	uchcom_ctrl_read(
 	    sc, UCHCOM_REQ_READ_REG,
@@ -433,7 +433,7 @@
 static void
 uchcom_get_version(struct uchcom_softc *sc, uint8_t *rver)
 {
-	uint8_t buf[UCHCOM_INPUT_BUF_SIZE];
+	uint8_t buf[UCHCOM_INPUT_BUF_SIZE] = {0};
 
 	uchcom_ctrl_read(sc, UCHCOM_REQ_GET_VERSION, 0, 0, buf, sizeof(buf));