Index: pyproject.toml
--- pyproject.toml.orig
+++ pyproject.toml
@@ -14,8 +14,8 @@ html2text = ">=2020.1.16"
 update-copyright = ">=0.6.2"
 
 [build-system]
-requires = ["poetry>=0.12"]
-build-backend = "poetry.masonry.api"
+requires = ["poetry-core>=0.12"]
+build-backend = "poetry.core.masonry.api"
 
 [tool.poetry.scripts]
 r2e = "rss2email.main:run"