diff --git a/pyproject.toml b/pyproject.toml
index 3d70ac9..40d17ee 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -5,7 +5,7 @@ authors = [{name = "Substrait contributors", email = "substrait@googlegroups.com
 license = {text = "Apache-2.0"}
 readme = "README.md"
 requires-python = ">=3.8.1"
-dependencies = ["protobuf >= 3.20"]
+dependencies = ["protobuf >= 3.20", "protobuf-c >= 3.20"]
 dynamic = ["version"]
 
 [tool.setuptools_scm]