diff --git a/sys/dev/fdt/fdt_common.c b/sys/dev/fdt/fdt_common.c
--- a/sys/dev/fdt/fdt_common.c
+++ b/sys/dev/fdt/fdt_common.c
@@ -441,6 +441,7 @@
 	reservep = (pcell_t *)&reserve;
 	for (i = 0; i < tuples; i++) {
 
+		memset(&mr, 0, sizeof(mr));
 		rv = fdt_data_to_res(reservep, addr_cells, size_cells,
 			(u_long *)&mr.mr_start, (u_long *)&mr.mr_size);
 
@@ -484,6 +485,7 @@
 			/* XXX: Does a no-map of a dynamic range make sense? */
 			continue;
 
+		memset(&mr, 0, sizeof(mr));
 		fdt_data_to_res(reg, addr_cells, size_cells,
 		    (u_long *)&mr.mr_start, (u_long *)&mr.mr_size);
 
@@ -526,6 +528,7 @@
 	regp = (pcell_t *)&reg;
 	for (i = 0; i < tuples; i++) {
 
+		memset(&mr, 0, sizeof(mr));
 		rv = fdt_data_to_res(regp, addr_cells, size_cells,
 			(u_long *)&mr.mr_start, (u_long *)&mr.mr_size);