diff --git a/src/apps/common/address_type.py b/src/apps/common/address_type.py
new file mode 100644
index 0000000000..53abbceff8
--- /dev/null
+++ b/src/apps/common/address_type.py
@@ -0,0 +1,27 @@
+def length(address_type):
+    if address_type <= 0xFF:
+        return 1
+    if address_type <= 0xFFFF:
+        return 2
+    if address_type <= 0xFFFFFF:
+        return 3
+    # else
+    return 4
+
+
+def check(address_type, raw_address):
+    if address_type <= 0xFF:
+        return address_type == raw_address[0]
+    if address_type <= 0xFFFF:
+        return address_type == (raw_address[0] << 8) | raw_address[1]
+    if address_type <= 0xFFFFFF:
+        return address_type == (raw_address[0] << 16) | (raw_address[1] << 8) | raw_address[2]
+    # else
+    return address_type == (raw_address[0] << 24) | (raw_address[1] << 16) | (raw_address[2] << 8) | raw_address[3]
+
+
+def strip(address_type, raw_address):
+    if not check(address_type, raw_address):
+        raise ValueError('Invalid address')
+    l = length(address_type)
+    return raw_address[l:]
diff --git a/src/apps/common/signtx.py b/src/apps/common/signtx.py
index 1584c7da55..66c4120485 100644
--- a/src/apps/common/signtx.py
+++ b/src/apps/common/signtx.py
@@ -2,6 +2,7 @@ from trezor.crypto.hashlib import sha256, ripemd160
 from trezor.crypto.curve import secp256k1
 from trezor.crypto import base58, der
 
+from . import address_type
 from . import coins
 
 from trezor.messages.CoinType import CoinType
@@ -312,25 +313,15 @@ def get_tx_hash(w, double: bool, reverse: bool=False) -> bytes:
 # TX Outputs
 # ===
 
-def len_address_type(address_type):
-    if address_type <= 0xFF:
-        return 1
-    if address_type <= 0xFFFF:
-        return 2
-    if address_type <= 0xFFFFFF:
-        return 3
-    # else
-    return 4
-
 def output_derive_script(o: TxOutputType, coin: CoinType, root) -> bytes:
     if o.script_type == OutputScriptType.PAYTOADDRESS:
         ra = output_paytoaddress_extract_raw_address(o, coin, root)
-        at = len_address_type(coin.address_type)
-        return script_paytoaddress_new(ra[at:])
+        ra = address_type.strip(coin.address_type, ra)
+        return script_paytoaddress_new(ra)
     elif o.script_type == OutputScriptType.PAYTOSCRIPTHASH:
         ra = output_paytoaddress_extract_raw_address(o, coin, root, p2sh=True)
-        at = len_address_type(coin.address_type_p2sh)
-        return script_paytoscripthash_new(ra[at:])
+        ra = address_type.strip(coin.address_type_p2sh, ra)
+        return script_paytoscripthash_new(ra)
     elif o.script_type == OutputScriptType.PAYTOOPRETURN:
         if o.amount == 0:
             return script_paytoopreturn_new(o.op_return_data)
@@ -343,28 +334,18 @@ def output_derive_script(o: TxOutputType, coin: CoinType, root) -> bytes:
     return
 
 
-def check_address_type(address_type, raw_address):
-    if address_type <= 0xFF:
-        return address_type == raw_address[0]
-    if address_type <= 0xFFFF:
-        return address_type == (raw_address[0] << 8) | raw_address[1]
-    if address_type <= 0xFFFFFF:
-        return address_type == (raw_address[0] << 16) | (raw_address[1] << 8) | raw_address[2]
-    # else
-    return address_type == (raw_address[0] << 24) | (raw_address[1] << 16) | (raw_address[2] << 8) | raw_address[3]
-
 def output_paytoaddress_extract_raw_address(o: TxOutputType, coin: CoinType, root, p2sh=False) -> bytes:
-    address_type = coin.address_type_p2sh if p2sh else coin.address_type
+    addr_type = coin.address_type_p2sh if p2sh else coin.address_type
     # TODO: dont encode/decode more then necessary
     address_n = getattr(o, 'address_n', None)
     if address_n is not None:
         node = node_derive(root, address_n)
-        address = node.address(address_type)
+        address = node.address(addr_type)
         return base58.decode_check(address)
     address = getattr(o, 'address', None)
     if address:
         raw = base58.decode_check(address)
-        if not check_address_type(address_type, raw):
+        if not address_type.check(addr_type, raw):
             raise SigningError(FailureType.SyntaxError,
                                'Invalid address type')
         return raw