diff --git a/pyproject.toml b/pyproject.toml
index ad8d2fb..3b3d60f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [build-system]
-requires = ["flit"]
-build-backend = "flit.buildapi"
+requires = ["flit_core >=2,<4"]
+build-backend = "flit_core.buildapi"
 
 [tool.flit.metadata]
 module = "submark"
@@ -14,4 +14,4 @@ classifiers = ["License :: OSI Approved :: MIT License"]
 test = ["pytest", "pytest-cov", "tox"]
 
 [tool.flit.scripts]
-submark = "submark:main"
\ No newline at end of file
+submark = "submark:main"