diff --git a/domaintools/api.py b/domaintools/api.py
index 22a0849..5df9c6c 100644
--- a/domaintools/api.py
+++ b/domaintools/api.py
@@ -1,5 +1,5 @@
 from datetime import datetime, timedelta, timezone
-from hashlib import sha1, sha256, md5
+from hashlib import sha1, sha256
 from hmac import new as hmac
 
 import re
@@ -24,7 +24,7 @@
 from domaintools.utils import validate_feeds_parameters
 
 
-AVAILABLE_KEY_SIGN_HASHES = ["sha1", "sha256", "md5"]
+AVAILABLE_KEY_SIGN_HASHES = ["sha1", "sha256"]
 
 
 def delimited(items, character="|"):
diff --git a/tests/test_api.py b/tests/test_api.py
index 3876d02..a54f1db 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -342,11 +342,20 @@ def test_exception_handling():
         API("notauser", "notakey").domain_search("amazon").data()
     with pytest.raises(
         ValueError,
-        match=r"Invalid value 'notahash' for 'key_sign_hash'. Values available are sha1,sha256,md5",
+        match=r"Invalid value 'notahash' for 'key_sign_hash'. Values available are sha1,sha256",
     ):
         API("notauser", "notakey", always_sign_api_key=True, key_sign_hash="notahash").domain_search("amazon")
 
 
+@vcr.use_cassette
+def test_md5_is_not_supported():
+    with pytest.raises(
+        ValueError,
+        match=r"Invalid value 'md5' for 'key_sign_hash'. Values available are sha1,sha256",
+    ):
+        API("notauser", "notakey", always_sign_api_key=True, key_sign_hash="md5").domain_search("amazon")
+
+
 @vcr.use_cassette
 def test_rate_limiting():
     domain_searches = ["google"] * 31
diff --git a/tox.ini b/tox.ini
index e7c06b0..a2a042e 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,12 +1,16 @@
 [tox]
-envlist=py39, py310, py311
+envlist =
+    py39,
+    py310,
+    py311
 skip_missing_interpreters=true
 
 [testenv]
-passenv=
+passenv =
     TEST_USER
     TEST_KEY
-deps=
+deps =
+    click==8.1.8
     pytest
     pytest-cov
     httpx
@@ -14,5 +18,6 @@ deps=
     rich
     typer
     .
-commands=py.test -s --capture=sys  --cov=domaintools --cov=domaintools_async tests
+commands =
+    py.test -s --capture=sys  --cov=domaintools --cov=domaintools_async tests
     coverage html