diff --git a/project.toml b/project.toml
index 45c61e72..fb6b15ae 100644
--- a/project.toml
+++ b/project.toml
@@ -8,3 +8,7 @@ exclude = [
     ".github",
     ".vscode",
 ]
+
+[[ io.buildpacks.build.env ]]
+  name = "BP_CPYTHON_VERSION"
+  value = "3.10.*" # any valid semver constraints (e.g. 3.6.7, 3.*) are acceptable
diff --git a/runtime.txt b/runtime.txt
deleted file mode 100644
index cf14ed13..00000000
--- a/runtime.txt
+++ /dev/null
@@ -1 +0,0 @@
-python-3.10.x