diff --git a/requirements-dev.txt b/requirements-dev.txt
index 69c92e612c..0026f61160 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -1,12 +1,11 @@
---index-url https://pypi.python.org/simple/
-
 # Developer extra packages
 
 ### docs
-alabaster>=0.7.7
 # Newer sphinx needed for proper type hint support in docstrings
 sphinx>=3.0.0
 sphinxcontrib-napoleon>=0.5.0
+# sphinx-argparse 0.4.0 is the last version to support Python 3.9
+# see https://sphinx-argparse.readthedocs.io/en/latest/changelog.html#id3
 sphinx-argparse==0.4.0
 sphinx-book-theme<=1.1.2,>=1.0.0
 sphinx-copybutton==0.5.2
@@ -19,15 +18,11 @@ pytest-cov
 # @lbianchi-lbl: both pylint and astroid should be tightly pinned; see .pylint/idaes_transform.py for more info
 pylint==3.0.3
 astroid==3.0.3
-flake8
 black==24.3.0
 # pre-commit install, manage, and run pre-commit hooks
 pre-commit
 
 ### other/misc
-jsonschema
-jupyter_contrib_nbextensions
-snowballstemmer==1.2.1
 addheader>=0.2.2
 
 # this will install IDAES in editable mode using the dependencies defined under the `extras_require` tags defined in `setup.py`