diff --git a/pyproject.toml b/pyproject.toml
index 8508a4a..1e4cc9b 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -21,6 +21,7 @@ classifiers = [
 description = "CLI to convert yaml into ics."
 
 dependencies = [
+    "ics-vtimezones == 2020.1",
     "ics == 0.8.0.dev0",
     "python-dateutil >= 2.8",
     "pyyaml >= 6",