diff --git a/pyproject.toml b/pyproject.toml
index 8e709c2..7d56e09 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -39,8 +39,11 @@ pytest = "poetry run pytest tests/"
 
 [tool.poetry.dependencies]
 python = "^3.6"
-tomlkit = { version = "^0.6.0", optional = true }
-"ruamel.yaml" = { version = "^0.16.10", optional = true }
+tomlkit = [
+    { version = "^0.7.0", python = "^3.6,<=3.7", optional = true },
+    { version = "^0.12.2", python = ">=3.7,<4", optional = true }
+]
+"ruamel.yaml" = { version = "^0.17.16", optional = true }
 
 [tool.poetry.extras]
 toml = ["tomlkit"]