diff --git a/AnyReadable.zig b/AnyReadable.zig
index 5fed1551ab0d2298778b665505ce0705f6cd86c4..888e16edc09cc1771d96ad7c736d1407510415da 100644
--- a/AnyReadable.zig
+++ b/AnyReadable.zig
@@ -3,8 +3,8 @@ const std = @import("std");
 const nio = @import("./nio.zig");
 const AnyReadable = @This();
 
-readFn: *const fn (*anyopaque, []u8) anyerror!usize,
-state: *anyopaque,
+readFn: *const fn (*allowzero anyopaque, []u8) anyerror!usize,
+state: *allowzero anyopaque,
 
 pub fn read(r: *AnyReadable, buffer: []u8) !usize {
     return r.readFn(r.state, buffer);
diff --git a/fixed_buffer_stream.zig b/fixed_buffer_stream.zig
index e4b0f3426dfe04c7417bea07c97a5da4bc61a698..6216762979a0e1e33d9bb832ac0b1eec05475909 100644
--- a/fixed_buffer_stream.zig
+++ b/fixed_buffer_stream.zig
@@ -29,7 +29,7 @@ pub fn FixedBufferStream(comptime Buffer: type) type {
 
         pub fn anyReadable(self: *Self) nio.AnyReadable {
             const S = struct {
-                fn foo(s: *anyopaque, buffer: []u8) anyerror!usize {
+                fn foo(s: *allowzero anyopaque, buffer: []u8) anyerror!usize {
                     const fbs: *Self = @ptrCast(@alignCast(s));
                     return fbs.read(buffer);
                 }