diff --git a/src/superio/common/ssdt.c b/src/superio/common/ssdt.c
index 035f06a..a919aa5 100644
--- a/src/superio/common/ssdt.c
+++ b/src/superio/common/ssdt.c
@@ -127,11 +127,11 @@
 		if (!res || !res->base || !res->size)
 			continue;
 
-		snprintf(name, sizeof(name), "IO%XB", i);
+		snprintf(name, sizeof(name), "IO%zXB", i);
 		name[4] = '\0';
 		acpigen_write_name_integer(name, res->base);
 
-		snprintf(name, sizeof(name), "IO%XS", i);
+		snprintf(name, sizeof(name), "IO%zXS", i);
 		name[4] = '\0';
 		acpigen_write_name_integer(name, res->size);
 	}