diff --git a/scripts/build_spec.py b/scripts/build_spec.py
index ca8bbb6dd..0baa487c3 100644
--- a/scripts/build_spec.py
+++ b/scripts/build_spec.py
@@ -169,7 +169,7 @@ def objects_to_spec(functions: Dict[str, str],
     functions_spec = '\n\n'.join(functions.values())
     for k in list(constants.keys()):
         if k.startswith('DOMAIN_'):
-            constants[k] = f"DomainType(({constants[k]}).to_bytes(length=4, byteorder='little'))"
+            constants[k] = f"DomainType(bytes.fromhex('{constants[k]}'[2:]))"
         if k == "BLS12_381_Q":
             constants[k] += "  # noqa: E501"
     constants_spec = '\n'.join(map(lambda x: '%s = %s' % (x, constants[x]), constants))
diff --git a/specs/core/0_beacon-chain.md b/specs/core/0_beacon-chain.md
index 71980e88c..271be3ef7 100644
--- a/specs/core/0_beacon-chain.md
+++ b/specs/core/0_beacon-chain.md
@@ -249,15 +249,13 @@ The following values are (non-configurable) constants used throughout the specif
 
 ### Domain types
 
-The following types are defined, mapping into `DomainType` (little endian):
-
 | Name | Value |
 | - | - |
-| `DOMAIN_BEACON_PROPOSER` | `0` |
-| `DOMAIN_BEACON_ATTESTER` | `1` |
-| `DOMAIN_RANDAO` | `2` |
-| `DOMAIN_DEPOSIT` | `3` |
-| `DOMAIN_VOLUNTARY_EXIT` | `4` |
+| `DOMAIN_BEACON_PROPOSER` | `0x00000000` |
+| `DOMAIN_BEACON_ATTESTER` | `0x01000000` |
+| `DOMAIN_RANDAO` | `0x02000000` |
+| `DOMAIN_DEPOSIT` | `0x03000000` |
+| `DOMAIN_VOLUNTARY_EXIT` | `0x04000000` |
 
 ## Containers
 
diff --git a/specs/core/1_custody-game.md b/specs/core/1_custody-game.md
index 017e2a22a..4f3b26c7c 100644
--- a/specs/core/1_custody-game.md
+++ b/specs/core/1_custody-game.md
@@ -131,7 +131,7 @@ The following types are defined, mapping into `DomainType` (little endian):
 
 | Name | Value |
 | - | - |
-| `DOMAIN_CUSTODY_BIT_CHALLENGE` | `6` |
+| `DOMAIN_CUSTODY_BIT_CHALLENGE` | `0x05000000` |
 
 ### TODO PLACEHOLDER
 
diff --git a/specs/core/1_shard-data-chains.md b/specs/core/1_shard-data-chains.md
index d5964fe7d..9d537a789 100644
--- a/specs/core/1_shard-data-chains.md
+++ b/specs/core/1_shard-data-chains.md
@@ -101,8 +101,8 @@ This document describes the shard transition function (data layer only) and the
 
 | Name | Value |
 | - | - |
-| `DOMAIN_SHARD_PROPOSER` | `128` |
-| `DOMAIN_SHARD_ATTESTER` | `129` |
+| `DOMAIN_SHARD_PROPOSER` | `0x80000000` |
+| `DOMAIN_SHARD_ATTESTER` | `0x81000000` |
 
 ## Containers