diff --git a/lib/std/Io.zig b/lib/std/Io.zig
index 7f945c8994be6556ae7c96b83457db7047274dea..9332633c8c854d3158ca439c541a4b0786448739 100644
--- a/lib/std/Io.zig
+++ b/lib/std/Io.zig
@@ -500,8 +500,8 @@ pub const Batch = struct {
     /// Returns the index that will be returned by `next` after the operation completes.
     /// Asserts that no more than `storage.len` operations are active at a time.
     pub fn add(batch: *Batch, operation: Operation) u32 {
-        const index = batch.unused.next;
-        batch.addAt(index.toIndex(), operation);
+        const index = batch.unused.head.toIndex();
+        batch.addAt(index, operation);
         return index;
     }
 
diff --git a/lib/std/Io/test.zig b/lib/std/Io/test.zig
index 62ad3c2ec8fc4b182b2071363fd13729c3c86043..73931f9ea9ba04facc1662da3e5ef4d1743b1bdf 100644
--- a/lib/std/Io/test.zig
+++ b/lib/std/Io/test.zig
@@ -692,14 +692,15 @@ test "read from a file using Batch.awaitAsync API" {
     var storage: [2]Io.Operation.Storage = undefined;
     var batch: Io.Batch = .init(&storage);
 
-    batch.addAt(0, .{ .file_read_streaming = .{
+    // Tests add API because this provides coverage for both add and addAt.
+    try testing.expectEqual(0, batch.add(.{ .file_read_streaming = .{
         .file = eyes_file,
         .data = &.{&eyes_buf},
-    } });
-    batch.addAt(1, .{ .file_read_streaming = .{
+    } }));
+    try testing.expectEqual(1, batch.add(.{ .file_read_streaming = .{
         .file = saviour_file,
         .data = &.{&saviour_buf},
-    } });
+    } }));
 
     // This API is supposed to *always* work even if the target has no
     // concurrency primitives available.