diff --git a/specs/test_formats/bls/msg_hash_g2_compressed.md b/specs/test_formats/bls/msg_hash_g2_compressed.md
index 44ea8ded7..bbc1b82fe 100644
--- a/specs/test_formats/bls/msg_hash_g2_compressed.md
+++ b/specs/test_formats/bls/msg_hash_g2_compressed.md
@@ -6,8 +6,8 @@ A BLS compressed-hash to G2.
 
 ```yaml
 input: 
-  message: bytes32,
-  domain: uint64 -- the BLS domain
+  message: bytes32
+  domain: bytes8   -- the BLS domain
 output: List[bytes48] -- length of two
 ```
 
diff --git a/specs/test_formats/bls/msg_hash_g2_uncompressed.md b/specs/test_formats/bls/msg_hash_g2_uncompressed.md
index 847b5f61d..8337baaab 100644
--- a/specs/test_formats/bls/msg_hash_g2_uncompressed.md
+++ b/specs/test_formats/bls/msg_hash_g2_uncompressed.md
@@ -7,7 +7,7 @@ A BLS uncompressed-hash to G2.
 ```yaml
 input: 
   message: bytes32
-  domain: uint64 -- the BLS domain
+  domain: bytes8   -- the BLS domain
 output: List[List[bytes48]] -- 3 lists, each a length of two
 ```
 
diff --git a/specs/test_formats/bls/sign_msg.md b/specs/test_formats/bls/sign_msg.md
index b17e6246d..8c6b8cdd0 100644
--- a/specs/test_formats/bls/sign_msg.md
+++ b/specs/test_formats/bls/sign_msg.md
@@ -8,7 +8,7 @@ Message signing with BLS should produce a signature.
 input:
   privkey: bytes32 -- the private key used for signing
   message: bytes32 -- input message to sign (a hash)
-  domain: uint64 -- the BLS domain
+  domain: bytes8   -- the BLS domain
 output: bytes96    -- expected signature
 ```
 
diff --git a/test_generators/bls/main.py b/test_generators/bls/main.py
index a792dda9a..284cf68b0 100644
--- a/test_generators/bls/main.py
+++ b/test_generators/bls/main.py
@@ -89,7 +89,7 @@ def case01_message_hash_G2_uncompressed():
             yield {
                 'input': {
                     'message': '0x' + msg.hex(),
-                    'domain': domain
+                    'domain': int_to_hex(domain, byte_length=8)
                 },
                 'output': hash_message(msg, domain)
             }
@@ -101,7 +101,7 @@ def case02_message_hash_G2_compressed():
             yield {
                 'input': {
                     'message': '0x' + msg.hex(),
-                    'domain': domain
+                    'domain': int_to_hex(domain, byte_length=8)
                 },
                 'output': hash_message_compressed(msg, domain)
             }
@@ -126,7 +126,7 @@ def case04_sign_messages():
                     'input': {
                         'privkey': int_to_hex(privkey),
                         'message': '0x' + message.hex(),
-                        'domain': domain
+                        'domain': int_to_hex(domain, byte_length=8)
                     },
                     'output': '0x' + sig.hex()
                 }