diff --git a/src/trezor/crypto/der.py b/src/trezor/crypto/der.py
index 8ad0564d63..6019116e13 100644
--- a/src/trezor/crypto/der.py
+++ b/src/trezor/crypto/der.py
@@ -1,4 +1,4 @@
-def encode_length(l: int):
+def encode_length(l: int) -> bytes:
     if l < 0x80:
        return bytes([l])
     elif l <= 0xFF:
@@ -8,13 +8,13 @@ def encode_length(l: int):
     else:
        raise ValueError
 
-def encode_int(i: bytes):
+def encode_int(i: bytes) -> bytes:
     i = i.lstrip(b'\x00')
     if i[0] >= 0x80:
         i = b'\x00' + i
     return b'\x02' + encode_length(len(i)) + i
 
-def encode_seq(seq: tuple):
+def encode_seq(seq: tuple) -> bytes:
     res = b''
     for i in seq:
         res += encode_int(i)
diff --git a/src/trezor/crypto/rlp.py b/src/trezor/crypto/rlp.py
index 13fb58d09c..4105ddfc64 100644
--- a/src/trezor/crypto/rlp.py
+++ b/src/trezor/crypto/rlp.py
@@ -1,4 +1,4 @@
-def to_binary(x: int):
+def int_to_bytes(x: int) -> bytes:
     if x == 0:
         return b''
     r = bytearray()
@@ -7,27 +7,28 @@ def to_binary(x: int):
         x //= 256
     return bytes(reversed(r))
 
-def encode_length(l: int, offset: int):
+def encode_length(l: int, is_list: bool) -> bytes:
+    offset = 0xC0 if is_list else 0x80
     if l < 56:
          return bytes([l + offset])
     elif l < 256 ** 8:
-         bl = to_binary(l)
+         bl = int_to_bytes(l)
          return bytes([len(bl) + offset + 55]) + bl
     else:
          raise ValueError('Input too long')
 
-def encode(data):
+def encode(data) -> bytes:
     if isinstance(data, int):
-        return encode(to_binary(data))
+        return encode(int_to_bytes(data))
     if isinstance(data, bytes):
         if len(data) == 1 and ord(data) < 128:
             return data
         else:
-            return encode_length(len(data), 128) + data
+            return encode_length(len(data), is_list=False) + data
     elif isinstance(data, list):
         output = b''
         for item in data:
             output += encode(item)
-        return encode_length(len(output), 192) + output
+        return encode_length(len(output), is_list=True) + output
     else:
         raise TypeError('Invalid input')