--- a/Cargo.toml
+++ b/Cargo.toml
@@ -22,7 +22,7 @@ license = "MIT"
 repository = "https://github.com/davidhewitt/pythonize"
 
 [dependencies.pyo3]
-version = "0.19.0"
+version = "0.17.3"
 default-features = false
 
 [dependencies.serde]
@@ -34,7 +34,7 @@ default-features = false
 version = "1.0.2"
 
 [dev-dependencies.pyo3]
-version = "0.19.0"
+version = "0.17.3"
 features = [
     "auto-initialize",
     "macros",