diff --git a/lib/libc/tests/stdio/print_positional_test.c b/lib/libc/tests/stdio/print_positional_test.c
index 1de43a1b499f..9c9ec314d62d 100644
--- a/lib/libc/tests/stdio/print_positional_test.c
+++ b/lib/libc/tests/stdio/print_positional_test.c
@@ -32,6 +32,7 @@
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
+#include <sys/param.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -94,7 +95,7 @@ ATF_TC_WITHOUT_HEAD(positional_wide);
 ATF_TC_BODY(positional_wide, tc)
 {
 
-	swprintf(wbuf1, sizeof wbuf1,
+	swprintf(wbuf1, nitems(wbuf1),
 	    L"|xx %1$s %2$s %3$s %4$s\n"
 	    "|xx %5$s %6$s %7$s %8$s\n"
 	    "|xx %9$s %10$s %11$s %12$s\n"
@@ -117,7 +118,7 @@ ATF_TC_BODY(positional_wide, tc)
 	    "43", "44", 45, -1L, 1LL, -1, 1LL
 	    );
 	temp = correct;
-	mbsrtowcs(wbuf2, &temp, sizeof wbuf2, NULL);
+	mbsrtowcs(wbuf2, &temp, nitems(wbuf2), NULL);
 	ATF_REQUIRE_MSG(wcscmp(wbuf1, wbuf2) == 0,
 	    "buffers didn't match");
 }
@@ -139,7 +140,7 @@ ATF_TC_BODY(positional_precision_wide, tc)
 	swprintf(wbuf1, sizeof buf, L"%2$.*4$s %2$.*3$s %1$s",
 		 "BSD", "bsd", 2, 1);
 	temp = correct2;
-	mbsrtowcs(wbuf2, &temp, sizeof wbuf2, NULL);
+	mbsrtowcs(wbuf2, &temp, nitems(wbuf2), NULL);
 	ATF_REQUIRE_MSG(wcscmp(wbuf1, wbuf2) == 0,
 	    "buffers didn't match");
 }