diff --git a/test_libs/pyspec/eth2spec/debug/encode.py b/test_libs/pyspec/eth2spec/debug/encode.py
index 670f580b2..9080bb573 100644
--- a/test_libs/pyspec/eth2spec/debug/encode.py
+++ b/test_libs/pyspec/eth2spec/debug/encode.py
@@ -1,10 +1,10 @@
 from eth2spec.utils.ssz.ssz_impl import hash_tree_root
 from eth2spec.utils.ssz.ssz_typing import (
-    SSZValue, uint, Container, boolean
+    uint, Container, boolean
 )
 
 
-def encode(value: SSZValue, include_hash_tree_roots=False):
+def encode(value, include_hash_tree_roots=False):
     if isinstance(value, uint):
         # Larger uints are boxed and the class declares their byte length
         if value.type().byte_len > 8:
diff --git a/test_libs/pyspec/eth2spec/test/utils.py b/test_libs/pyspec/eth2spec/test/utils.py
index bc91053e8..253691764 100644
--- a/test_libs/pyspec/eth2spec/test/utils.py
+++ b/test_libs/pyspec/eth2spec/test/utils.py
@@ -29,12 +29,12 @@ def spectest(description: str = None):
                         (key, value, typ) = data
                         out[key] = encode(value, typ)
                     else:
-                        # Otherwise, try to infer the type, but keep it as-is if it's not a SSZ container.
+                        # Otherwise, try to infer the type, but keep it as-is if it's not a SSZ type or bytes.
                         (key, value) = data
-                        if isinstance(value, SSZValue):
-                            out[key] = encode(value, value.__class__)
-                        elif isinstance(value, list) and all([isinstance(el, SSZValue) for el in value]):
-                            out[key] = [encode(el, el.__class__) for el in value]
+                        if isinstance(value, (SSZValue, bytes)):
+                            out[key] = encode(value)
+                        elif isinstance(value, list) and all([isinstance(el, (SSZValue, bytes)) for el in value]):
+                            out[key] = [encode(el) for el in value]
                         else:
                             # not a ssz value.
                             # It could be vector or bytes still, but it is a rare case,