diff --git a/scripts/ci.requirements.txt b/scripts/ci.requirements.txt
index 9b96a8d..e779483 100644
--- a/scripts/ci.requirements.txt
+++ b/scripts/ci.requirements.txt
@@ -12,3 +12,7 @@
 # Use the earliest version of mypy that works with our code base.
 # See https://github.com/Mbed-TLS/mbedtls/pull/3953 .
 mypy >= 0.780
+
+# For building `tests/data_files/server9-bad-saltlen.crt` and check python
+# files.
+asn1crypto
diff --git a/scripts/maintainer.requirements.txt b/scripts/maintainer.requirements.txt
index 4256354..8734140 100644
--- a/scripts/maintainer.requirements.txt
+++ b/scripts/maintainer.requirements.txt
@@ -9,6 +9,3 @@
 # For building some test vectors
 pycryptodomex
 pycryptodome-test-vectors
-
-# For building `tests/data_files/server9-bad-saltlen.crt`
-asn1crypto