diff --git a/README.md b/README.md
index 492c3c04bb8e6ba75e4e2149855e497df1b92d00..dd6d9d39c7d83775bdb1ed880a9fb1fe0f39bce2 100644
--- a/README.md
+++ b/README.md
@@ -3,7 +3,7 @@
 ![loc](https://sloc.xyz/github/nektro/zig-totp)
 [![license](https://img.shields.io/github/license/nektro/zig-totp.svg)](https://github.com/nektro/zig-totp/blob/master/LICENSE)
 [![nektro @ github sponsors](https://img.shields.io/badge/sponsors-nektro-purple?logo=github)](https://github.com/sponsors/nektro)
-[![Zig](https://img.shields.io/badge/Zig-0.15-f7a41d)](https://ziglang.org/)
+[![Zig](https://img.shields.io/badge/Zig-0.16-f7a41d)](https://ziglang.org/)
 [![Zigmod](https://img.shields.io/badge/Zigmod-latest-f7a41d)](https://github.com/nektro/zigmod)
 
 RFC 6238: TOTP: Time-Based One-Time Password Algorithm
diff --git a/build.zig b/build.zig
index fe5b54594c752343ec4acc64a2db5d0740e36883..691ea5f05fe8afee54f787f133ee48b396977f8f 100644
--- a/build.zig
+++ b/build.zig
@@ -14,6 +14,7 @@ pub fn build(b: *std.Build) void {
         }),
     });
     deps.addAllTo(tests);
+    tests.root_module.link_libc = true;
     tests.use_llvm = !disable_llvm;
     tests.use_lld = !disable_llvm;
     b.getInstallStep().dependOn(&tests.step);
diff --git a/totp.zig b/totp.zig
index 83f22e500a3662110c3a50942c9286f0540e2656..f862f9a691672748822ed08823a77cafb7b4a398 100644
--- a/totp.zig
+++ b/totp.zig
@@ -1,6 +1,7 @@
 const std = @import("std");
 const extras = @import("extras");
 const url = @import("url");
+const nio = @import("nio");
 
 pub fn totp(digits: comptime_int, Hash: type, epoch: u64, X: u64, K: *const [Hash.digest_length]u8, time_now_s: u64) [digits]u8 {
     const T = (time_now_s - epoch) / X;
@@ -56,32 +57,32 @@ pub fn generateUrl(allocator: std.mem.Allocator, issuer: []const u8, account: []
     std.debug.assert(secret_raw.len <= algo.digest_length());
     std.debug.assert(digits == 6 or digits == 7 or digits == 8);
     std.debug.assert(period == 15 or period == 30 or period == 60);
-    var list: std.array_list.Managed(u8) = .init(allocator);
+    var list: nio.AllocatingWriter = .init(allocator);
     errdefer list.deinit();
-    try list.appendSlice("otpauth://");
-    try list.appendSlice("totp/");
+    try list.writeAll("otpauth://");
+    try list.writeAll("totp/");
     try url.percentEncodeAL(&list, issuer, url.is_path_percent_char);
-    try list.append(':');
+    try list.writeAll(":");
     try url.percentEncodeAL(&list, account, url.is_path_percent_char);
-    try list.appendSlice("?secret=");
+    try list.writeAll("?secret=");
     try encodeBase32(&list, secret_raw);
-    try list.appendSlice("&algorithm=");
-    try list.appendSlice(@tagName(algo));
-    try list.appendSlice("&digits=");
-    try list.writer().print("{d}", .{digits});
-    try list.appendSlice("&period=");
-    try list.writer().print("{d}", .{period});
-    try list.appendSlice("&issuer=");
+    try list.writeAll("&algorithm=");
+    try list.writeAll(@tagName(algo));
+    try list.writeAll("&digits=");
+    try list.print("{d}", .{digits});
+    try list.writeAll("&period=");
+    try list.print("{d}", .{period});
+    try list.writeAll("&issuer=");
     try url.percentEncodeAL(&list, issuer, url.is_query_percent_char);
     return list.toOwnedSlice();
 }
 
 // RFC3548 base32
 // input.len is gonna be 64 | 32 | 64
-fn encodeBase32(list: *std.array_list.Managed(u8), input: []const u8) !void {
+fn encodeBase32(list: *nio.AllocatingWriter, input: []const u8) !void {
     const alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
     var iter = BufBiterator.init(input);
-    while (iter.nextInt(u5)) |idx| try list.append(alphabet[idx]);
+    while (iter.nextInt(u5)) |idx| try list.writeAll(alphabet[idx..][0..1]);
 }
 
 const BufBiterator = struct {
diff --git a/zigmod.yml b/zigmod.yml
index df50742a403c0363841b77dc83cb4565218d95f6..583ef4e16e89fbe1c221d01f162ee45357c1e8c9 100644
--- a/zigmod.yml
+++ b/zigmod.yml
@@ -6,6 +6,7 @@ description: "RFC 6238: TOTP: Time-Based One-Time Password Algorithm"
 dependencies:
   - src: git https://github.com/nektro/zig-extras
   - src: git https://github.com/nektro/zig-whatwg-url
+  - src: git https://github.com/nektro/zig-nio
 root_dependencies:
   - src: git https://github.com/nektro/zig-extras
   - src: git https://github.com/nektro/zig-expect