diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index eaa50ac..fe1e5cc 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -11,7 +11,7 @@ test:
     - tags
   script:
     - make venv
-    - env/bin/pip install setuptools
+    - env/bin/pip install 'setuptools<81'
     - make test
 
 build:
@@ -21,7 +21,7 @@ build:
     - tags
   script:
     - make venv
-    - env/bin/pip install setuptools
+    - env/bin/pip install 'setuptools<81'
     - make install-source-prod
     # Copy static assets to env/static
     - cp -pr remarkbox/static env/static
diff --git a/Makefile b/Makefile
index 6e938bb..4f03dd1 100644
--- a/Makefile
+++ b/Makefile
@@ -24,7 +24,7 @@ $(VENV_DIR)/bin/activate:
 	@echo "Creating virtual environment in $(VENV_DIR)..."
 	python3 -m venv $(VENV_DIR)
 	@echo "Installing setuptools (required by Pyramid, not bundled in Python 3.12+ venvs)..."
-	$(PIP) install setuptools
+	$(PIP) install 'setuptools<81'
 
 venv: $(VENV_DIR)/bin/activate
 
@@ -66,7 +66,7 @@ install: install-core install-dev install-themes
 # Install remarkbox from source (editable mode) plus dev, test, and themes
 install-source-dev-and-test: venv install-themes
 	@echo "Ensuring setuptools is installed (required by Pyramid on Python 3.12+)..."
-	$(PIP) install setuptools
+	$(PIP) install 'setuptools<81'
 	@echo "Installing remarkbox from source (editable mode)..."
 	$(PIP) install --editable .
 	$(PIP) install --upgrade -r requirements-dev.txt
@@ -74,7 +74,7 @@ install-source-dev-and-test: venv install-themes
 
 install-source-prod: venv install-themes
 	@echo "Ensuring setuptools is installed (required by Pyramid on Python 3.12+)..."
-	$(PIP) install setuptools
+	$(PIP) install 'setuptools<81'
 	@echo "Deleting tests from source code for production..."
 	rm -rf remarkbox/tests
 	@echo "Installing remarkbox from source (in non-editable mode)..."
diff --git a/requirements.py3.txt b/requirements.py3.txt
index d38b1c6..35cb65b 100644
--- a/requirements.py3.txt
+++ b/requirements.py3.txt
@@ -2,8 +2,8 @@
 six
 
 # Python 3.12+ no longer bundles setuptools in venvs.
-# Pyramid imports pkg_resources which lives in setuptools.
-setuptools
+# Pyramid imports pkg_resources which was removed in setuptools 81+.
+setuptools<81
 
 # Pyramid.
 plaster_pastedeploy