diff --git a/lib/libthr/thread/thr_printf.c b/lib/libthr/thread/thr_printf.c
--- a/lib/libthr/thread/thr_printf.c
+++ b/lib/libthr/thread/thr_printf.c
@@ -61,7 +61,10 @@
 void
 _thread_vprintf(int fd, const char *fmt, va_list ap)
 {
-	static const char digits[16] = "0123456789abcdef";
+	static const char digits[16] = {
+	    '0', '1', '2', '3', '4', '5', '6', '7',
+	    '8', '9', 'a', 'b', 'c', 'd', 'e', 'f',
+	};
 	char buf[20];
 	char *s;
 	unsigned long r, u;
@@ -147,4 +150,3 @@
 
 	__sys_write(fd, s, strlen(s));
 }
-