Index: pep508-rs/Cargo.toml
===================================================================
--- pep508-rs.orig/Cargo.toml
+++ pep508-rs/Cargo.toml
@@ -51,7 +51,7 @@ version = "1.18.0"
 version = "0.3.11"
 
 [dependencies.pyo3]
-version = "0.19.2"
+version = ">=0.18, <0.21"
 features = [
     "abi3",
     "extension-module",
