diff --git a/environment.yml b/environment.yml
index e46f745e3..869685fe5 100644
--- a/environment.yml
+++ b/environment.yml
@@ -23,6 +23,7 @@ dependencies:
 - pip
 - yosys
 - netlistsvg
+- ngspice
 # Packages installed from PyPI
 - pip:
   - -r file:requirements.txt
diff --git a/requirements.txt b/requirements.txt
index fe8a2c1b2..1418887e7 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -4,5 +4,8 @@ flake8
 # previews.
 rst_include
 
+# the PySpice module for rendering FET bins plots
+PySpice==1.4.3
+
 # The Python API for the SkyWater PDK.
 -e scripts/python-skywater-pdk