diff --git a/test/behavior.zig b/test/behavior.zig
index 9e01526d1d..c632d39eb9 100644
--- a/test/behavior.zig
+++ b/test/behavior.zig
@@ -100,6 +100,7 @@ test {
     _ = @import("behavior/bugs/12488.zig");
     _ = @import("behavior/bugs/12498.zig");
     _ = @import("behavior/bugs/12551.zig");
+    _ = @import("behavior/bugs/12571.zig");
     _ = @import("behavior/bugs/12644.zig");
     _ = @import("behavior/bugs/12680.zig");
     _ = @import("behavior/bugs/12723.zig");
diff --git a/test/behavior/bugs/12571.zig b/test/behavior/bugs/12571.zig
new file mode 100644
index 0000000000..4338051b18
--- /dev/null
+++ b/test/behavior/bugs/12571.zig
@@ -0,0 +1,22 @@
+const builtin = @import("builtin");
+const std = @import("std");
+const expect = std.testing.expect;
+
+const Frame = packed struct {
+    num: u20,
+};
+
+const Entry = packed struct {
+    other: u12,
+    frame: Frame,
+};
+
+test {
+    if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
+
+    const frame = Frame{ .num = 0x7FDE };
+    var entry = Entry{ .other = 0, .frame = .{ .num = 0xFFFFF } };
+    entry.frame = frame;
+    try expect(entry.frame.num == 0x7FDE);
+}