diff --git a/sbe/__init__.py b/sbe/__init__.py
index 6d3e769..73a1081 100644
--- a/sbe/__init__.py
+++ b/sbe/__init__.py
@@ -7,6 +7,7 @@
 import lxml
 import lxml.etree
 
+
 class PrimitiveType(enum.Enum):
     CHAR = 'char'
     UINT8 = 'uint8'
@@ -281,10 +282,10 @@ def encode(self, vals: Iterable[str]) -> int:
         return bitstring.BitArray(v.name in vals for v in reversed(self.choices)).uint
 
     def decode(self, val: int) -> List[str]:
-        if isinstance(self.encodingType, SetEncodingType):
-            length = FORMAT_SIZES[PrimitiveType[self.encodingType.name]] * 8
-        else:
-            length = FORMAT_SIZES[self.encodingType.primitiveType] * 8
+        # if isinstance(self.encodingType, SetEncodingType):
+        #     length = FORMAT_SIZES[PrimitiveType[self.encodingType.name]] * 8
+        # else:
+        #     length = FORMAT_SIZES[self.encodingType.primitiveType] * 8
 
         return [c.name for c in self.choices if (1 << c.value) & val]
 
@@ -559,7 +560,7 @@ def wrap(self, buf: Union[bytes, memoryview], header_only=False) -> WrappedMessa
 
         return WrappedMessage(buf, header, body)
 
-    def create_wrappers(self) -> WrappedMessage:
+    def create_wrappers(self):
         cursor = Cursor(0)
 
         pointers = {}
@@ -573,7 +574,6 @@ def create_wrappers(self) -> WrappedMessage:
             _walk_fields_wrap(self, pointers, m.fields, cursor)
             self.message_wrappers[i] = WrappedComposite(m.name, pointers, None, 0)
 
-
 def _unpack_format(
     schema: Schema,
     type_: Union[Field, Group, PrimitiveType, Type, RefType, Set, Enum, Composite],
@@ -640,6 +640,7 @@ def _unpack_format(
     if isinstance(type_, Composite):
         return prefix + ''.join(_unpack_format(schema, t, '', buffer, buffer_cursor) for t in type_.types)
 
+    assert False, f"unreachable: {type_}"
 
 def _pack_format(_schema: Schema, composite: Composite):
     fmt = []
@@ -793,7 +794,7 @@ def _walk_fields_encode(schema: Schema, fields: List[Union[Group, Field]],
                 if t == PrimitiveType.CHAR:
                     vals.append(obj[f.name].encode())
                 else:
-                    vals.append(f.type.nullValue) if obj[f.name] is None else vals.append(obj[f.name])
+                    vals.append(obj[f.name] if obj[f.name] is not None else f.type.nullValue)
                 cursor.val += FORMAT_SIZES[t]
 
         elif isinstance(f.type, Set):
@@ -822,7 +823,7 @@ def _walk_fields_encode(schema: Schema, fields: List[Union[Group, Field]],
 
         elif isinstance(f.type, PrimitiveType):
             fmt.append(FORMAT[f.type])
-            vals.append(obj[f.name].encode()) if f.type == PrimitiveType.CHAR else vals.append(obj[f.name])
+            vals.append(obj[f.name].encode() if f.type == PrimitiveType.CHAR else obj[f.name])
             cursor.val += FORMAT_SIZES[f.type]
         else:
             assert 0