diff --git a/pyproject.toml b/pyproject.toml
index afc1b33..5f83abc 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -9,7 +9,7 @@ authors = [{ name = "Mr. Finchum" }]
 description = "User interface for OPTIMA35."
 readme = "README.md"
 requires-python = ">=3.8"
-dependencies = ["optima35", "pyside6"]
+dependencies = ["optima35==0.6.4", "pyside6", "PyYAML"]
 classifiers = [
     "Programming Language :: Python :: 3",
     "License :: OSI Approved :: GNU Affero General Public License v3 or later (AGPLv3+)",