diff --git a/lib/std/Io/Writer.zig b/lib/std/Io/Writer.zig
index 6c5798f7f8..131e7ea518 100644
--- a/lib/std/Io/Writer.zig
+++ b/lib/std/Io/Writer.zig
@@ -141,8 +141,14 @@ pub const failing: Writer = .{
         .sendFile = failingSendFile,
         .rebase = failingRebase,
     },
+    .buffer = &.{},
 };
 
+test failing {
+    var fw: Writer = .failing;
+    try testing.expectError(error.WriteFailed, fw.writeAll("always fails"));
+}
+
 /// Returns the contents not yet drained.
 pub fn buffered(w: *const Writer) []u8 {
     return w.buffer[0..w.end];