diff --git a/checks.c b/checks.c
index 4b72b53..afabf64 100644
--- a/checks.c
+++ b/checks.c
@@ -873,7 +873,7 @@ static void check_simple_bus_reg(struct check *c, struct dt_info *dti, struct no
 	while (size--)
 		reg = (reg << 32) | fdt32_to_cpu(*(cells++));
 
-	snprintf(unit_addr, sizeof(unit_addr), "%zx", reg);
+	snprintf(unit_addr, sizeof(unit_addr), "%"PRIx64, reg);
 	if (!streq(unitname, unit_addr))
 		FAIL(c, dti, "Node %s simple-bus unit address format error, expected \"%s\"",
 		     node->fullpath, unit_addr);
diff --git a/dtc.h b/dtc.h
index fc24e17..409db76 100644
--- a/dtc.h
+++ b/dtc.h
@@ -31,6 +31,7 @@
 #include <ctype.h>
 #include <errno.h>
 #include <unistd.h>
+#include <inttypes.h>
 
 #include <libfdt_env.h>
 #include <fdt.h>