diff --git a/src/embit/psbt.py b/src/embit/psbt.py
index 54497c2..0d7b095 100644
--- a/src/embit/psbt.py
+++ b/src/embit/psbt.py
@@ -142,6 +142,7 @@ def __init__(self, unknown: dict = {}, vin=None, compress=CompressMode.KEEP_ALL)
         self.taproot_bip32_derivations = OrderedDict()
         self.taproot_internal_key = None
         self.taproot_merkle_root = None
+        self.taproot_key_sig = None
         self.taproot_sigs = OrderedDict()
         self.taproot_scripts = OrderedDict()
 
@@ -187,6 +188,7 @@ def update(self, other):
         self.taproot_bip32_derivations.update(other.taproot_bip32_derivations)
         self.taproot_internal_key = other.taproot_internal_key
         self.taproot_merkle_root = other.taproot_merkle_root or self.taproot_merkle_root
+        self.taproot_key_sig = other.taproot_key_sig or self.taproot_key_sig
         self.taproot_sigs.update(other.taproot_sigs)
         self.taproot_scripts.update(other.taproot_scripts)
         self.final_scriptsig = other.final_scriptsig or self.final_scriptsig
@@ -350,7 +352,15 @@ def read_value(self, stream, k):
         elif k == b"\x10":
             self.sequence = int.from_bytes(v, "little")
 
-        # TODO: 0x13 - tap key signature
+        # PSBT_IN_TAP_KEY_SIG
+        elif k[0] == 0x13:
+            # read the taproot key sig
+            if len(k) != 1:
+                raise PSBTError("Invalid taproot key signature key")
+            if self.taproot_key_sig is not None:
+                raise PSBTError("Duplicated taproot key signature")
+            self.taproot_key_sig = v
+
         # PSBT_IN_TAP_SCRIPT_SIG
         elif k[0] == 0x14:
             if len(k) != 65:
@@ -434,6 +444,11 @@ def write_to(self, stream, skip_separator=False, version=None, **kwargs) -> int:
                 r += ser_string(stream, b"\x10")
                 r += ser_string(stream, self.sequence.to_bytes(4, "little"))
 
+        # PSBT_IN_TAP_KEY_SIG
+        if self.taproot_key_sig is not None:
+            r += ser_string(stream, b"\x13")
+            r += ser_string(stream, self.taproot_key_sig)
+        
         # PSBT_IN_TAP_SCRIPT_SIG
         for pub, leaf in self.taproot_sigs:
             r += ser_string(stream, b"\x14" + pub.xonly() + leaf)
@@ -881,11 +896,11 @@ def sign_input_with_tapkey(
                 sighash=sighash,
             )
             sig = pk.schnorr_sign(h)
-            wit = sig.serialize()
+            sigdata = sig.serialize()
             if sighash != SIGHASH.DEFAULT:
-                wit += bytes([sighash])
-            # TODO: maybe better to put into internal key sig field
-            inp.final_scriptwitness = Witness([wit])
+                sigdata += bytes([sighash])
+            inp.taproot_key_sig = sigdata
+            inp.final_scriptwitness = Witness([sigdata])
             # no need to sign anything else
             return 1
         counter = 0