diff --git a/lib/std/Io/Kqueue.zig b/lib/std/Io/Kqueue.zig
index 8d673525560c1898b7c1976979c0079feaebe676..63fd846b72abecaf75f44487d6023385b486d345 100644
--- a/lib/std/Io/Kqueue.zig
+++ b/lib/std/Io/Kqueue.zig
@@ -1401,9 +1401,9 @@ fn openSocketPosix(
     };
     errdefer closeFd(socket_fd);
 
-    if (options.ip6_only) {
+    if (options.ip6_only) |ip6_only| {
         if (posix.IPV6 == void) return error.OptionUnsupported;
-        try setSocketOption(k, socket_fd, posix.IPPROTO.IPV6, posix.IPV6.V6ONLY, 1);
+        try setSocketOption(k, socket_fd, posix.IPPROTO.IPV6, posix.IPV6.V6ONLY, @intFromBool(ip6_only));
     }
 
     return socket_fd;
diff --git a/lib/std/Io/Threaded.zig b/lib/std/Io/Threaded.zig
index 1b5db4d4dbdac8bb01b33b4a31b8356ad9970cd4..b23d0c1b23b52095af96cae95e186edcd377226a 100644
--- a/lib/std/Io/Threaded.zig
+++ b/lib/std/Io/Threaded.zig
@@ -12407,9 +12407,9 @@ fn openSocketPosix(
     };
     errdefer closeFd(socket_fd);
 
-    if (options.ip6_only) {
+    if (options.ip6_only) |ip6_only| {
         if (posix.IPV6 == void) return error.OptionUnsupported;
-        try setSocketOptionPosix(socket_fd, posix.IPPROTO.IPV6, posix.IPV6.V6ONLY, 1);
+        try setSocketOptionPosix(socket_fd, posix.IPPROTO.IPV6, posix.IPV6.V6ONLY, @intFromBool(ip6_only));
     }
 
     return socket_fd;
@@ -14496,7 +14496,7 @@ fn lookupDns(
     var socket = s: {
         if (any_ip6) ip6: {
             const ip6_addr: IpAddress = .{ .ip6 = .unspecified(0) };
-            const socket = ip6_addr.bind(t_io, .{ .ip6_only = true, .mode = .dgram }) catch |err| switch (err) {
+            const socket = ip6_addr.bind(t_io, .{ .ip6_only = false, .mode = .dgram }) catch |err| switch (err) {
                 error.AddressFamilyUnsupported => break :ip6,
                 else => |e| return e,
             };
diff --git a/lib/std/Io/Uring.zig b/lib/std/Io/Uring.zig
index 0b800682a154af8c9b31acbf36a555920ea09431..9184cd574153b4768c76347d4e246120827b4a26 100644
--- a/lib/std/Io/Uring.zig
+++ b/lib/std/Io/Uring.zig
@@ -5984,9 +5984,9 @@ fn socket(
     };
     errdefer ev.closeAsync(socket_fd);
 
-    if (options.ip6_only) {
+    if (options.ip6_only) |ip6_only| {
         if (linux.IPV6 == void) return error.OptionUnsupported;
-        try ev.setsockopt(cancel_region, socket_fd, linux.IPPROTO.IPV6, linux.IPV6.V6ONLY, 1);
+        try ev.setsockopt(cancel_region, socket_fd, linux.IPPROTO.IPV6, linux.IPV6.V6ONLY, @intFromBool(ip6_only));
     }
 
     return socket_fd;
diff --git a/lib/std/Io/net.zig b/lib/std/Io/net.zig
index 2115e73e4957c6cf91461918b0f3c4fcc7a2ccc2..c704d8b9e924da4578e447f9d3e5be3ad9f42533 100644
--- a/lib/std/Io/net.zig
+++ b/lib/std/Io/net.zig
@@ -281,7 +281,9 @@ pub const IpAddress = union(enum) {
         /// The socket is restricted to sending and receiving IPv6 packets only.
         /// In this case, an IPv4 and an IPv6 application can bind to a single port
         /// at the same time.
-        ip6_only: bool = false,
+        ///
+        /// The default is determined by system configuration.
+        ip6_only: ?bool = null,
         /// Allow the socket to send datagrams to broadcast addresses.
         /// When not enabled any attempt to send datagrams to a broadcast address
         /// will fail with `error.AccessDenied`