diff --git a/lib/libc/gdtoa/_hdtoa.c b/lib/libc/gdtoa/_hdtoa.c
index ff7ed5575be3..11fc93ec9765 100644
--- a/lib/libc/gdtoa/_hdtoa.c
+++ b/lib/libc/gdtoa/_hdtoa.c
@@ -55,7 +55,7 @@ roundup(char *s0, int ndigits)
 			*s = 1;
 			return (1);
 		}
-		++*s;
+		*s = 0;
 	}
 	++*s;
 	return (0);
diff --git a/lib/libc/stdio/vfprintf.c b/lib/libc/stdio/vfprintf.c
index 58e7a1f96101..e0c76af19f88 100644
--- a/lib/libc/stdio/vfprintf.c
+++ b/lib/libc/stdio/vfprintf.c
@@ -535,8 +535,8 @@ __vfprintf(FILE *fp, const char *fmt0, va_list ap)
 	static char zeroes[PADSIZE] =
 	 {'0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0'};
 
-	static const char xdigs_lower[17] = "0123456789abcdef?";
-	static const char xdigs_upper[17] = "0123456789ABCDEF?";
+	static const char xdigs_lower[16] = "0123456789abcdef";
+	static const char xdigs_upper[16] = "0123456789ABCDEF";
 
 	/*
 	 * BEWARE, these `goto error' on error, and PAD uses `n'.