diff --git a/tests/test_roundtrip_interpolated.py b/tests/test_roundtrip_interpolated.py
new file mode 100644
index 0000000..31320a5
--- /dev/null
+++ b/tests/test_roundtrip_interpolated.py
@@ -0,0 +1,38 @@
+from codex32 import Codex32String
+
+def test_round_trip_recovery():
+    # secret share from seed
+    s = Codex32String.from_seed(bytes.fromhex("68f14219957131d21b615271058437e8"), "ms13k00ls")
+    assert s.s == "ms13k00lsdrc5yxv4wycayxmp2fcstppharks8z0r84pf3uj"
+
+    # derive 'a' via proposed BIP-85
+    a = Codex32String.from_seed(bytes.fromhex("641be1cb12c97ede1c6bad8edf067760"), "ms13k00la")
+    assert a.s == "ms13k00lavsd7rjcje9ldu8rt4k8d7pnhvppyrt5gpff9wwl"
+
+    # derive 'c' via proposed BIP-85
+    c = Codex32String.from_seed(bytes.fromhex("61b3c4052f7a31dc2b425c843a13c9b4"), "ms13k00lc")
+    assert c.s == "ms13k00lcvxeugpf00gcac26ztjzr5y7fkjl7fx7nx7ykhkr"
+
+    # derive next share via interpolation
+    d = Codex32String.interpolate_at([s, a, c], "d")
+    assert d.s == "ms13k00ldp4v5nw8lph96x47mjxzgwjexe44p32swkq99e0w"
+
+    # now round-trip d share ('d' is derived via interpolation, NOT via 'from_seed')
+    dd = Codex32String.from_seed(d.data, "ms13k00ld", d.pad_val)
+    assert dd.s == d.s
+
+    e = Codex32String.interpolate_at([s, a, c], "e")
+    assert e.s == "ms13k00lezuknydaaygk5u20zs4fm736vj909mdj6xqp8pc2"
+    
+    f = Codex32String.interpolate_at([s, a, c], "f")
+    assert f.s == "ms13k00lf0ehe53zsu6vrxcjjh9v7wzsa83mqfvku3fd8kem"
+
+    # recover from shares, use 'd' without round-trip
+    rec_s = Codex32String.interpolate_at([a, c, d], "s")
+    # recover from shares, use 'd' after round-trip
+    rec_ss = Codex32String.interpolate_at([a, c, dd], "s")
+
+    assert s.data == rec_s.data
+    assert s.data == rec_ss.data
+    
+