diff --git a/dev-requirements.txt b/dev-requirements.txt
index 20b9f44..f52b6f2 100644
--- a/dev-requirements.txt
+++ b/dev-requirements.txt
@@ -1,3 +1,7 @@
+# Core dependencies pinned at their latest versions for tests and dev
+dataclasses==0.8 ; python_version < '3.7'
+pylangacq==0.14.0
+wordseg==0.0.2
 # For tests, style checks, and deployment
 black==20.8b1
 flake8==3.8.4