diff --git a/Cargo.lock b/Cargo.lock
index 9c5a8ef..0b4abce 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2377,11 +2377,10 @@ dependencies = [
 
 [[package]]
 name = "pyo3"
-version = "0.23.5"
+version = "0.25.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7778bffd85cf38175ac1f545509665d0b9b92a198ca7941f131f85f7a4f9a872"
+checksum = "8970a78afe0628a3e3430376fc5fd76b6b45c4d43360ffd6cdd40bdde72b682a"
 dependencies = [
- "cfg-if",
  "chrono",
  "indoc",
  "libc",
@@ -2396,9 +2395,9 @@ dependencies = [
 
 [[package]]
 name = "pyo3-async-runtimes"
-version = "0.23.0"
+version = "0.25.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "977dc837525cfd22919ba6a831413854beb7c99a256c03bf8624ad707e45810e"
+checksum = "d73cc6b1b7d8b3cef02101d37390dbdfe7e450dfea14921cae80a9534ba59ef2"
 dependencies = [
  "async-channel",
  "futures",
@@ -2410,9 +2409,9 @@ dependencies = [
 
 [[package]]
 name = "pyo3-build-config"
-version = "0.23.5"
+version = "0.25.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "94f6cbe86ef3bf18998d9df6e0f3fc1050a8c5efa409bf712e661a4366e010fb"
+checksum = "458eb0c55e7ece017adeba38f2248ff3ac615e53660d7c71a238d7d2a01c7598"
 dependencies = [
  "once_cell",
  "target-lexicon",
@@ -2420,9 +2419,9 @@ dependencies = [
 
 [[package]]
 name = "pyo3-ffi"
-version = "0.23.5"
+version = "0.25.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e9f1b4c431c0bb1c8fb0a338709859eed0d030ff6daa34368d3b152a63dfdd8d"
+checksum = "7114fe5457c61b276ab77c5055f206295b812608083644a5c5b2640c3102565c"
 dependencies = [
  "libc",
  "pyo3-build-config",
@@ -2441,9 +2440,9 @@ dependencies = [
 
 [[package]]
 name = "pyo3-macros"
-version = "0.23.5"
+version = "0.25.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fbc2201328f63c4710f68abdf653c89d8dbc2858b88c5d88b0ff38a75288a9da"
+checksum = "a8725c0a622b374d6cb051d11a0983786448f7785336139c3c94f5aa6bef7e50"
 dependencies = [
  "proc-macro2",
  "pyo3-macros-backend",
@@ -2453,9 +2452,9 @@ dependencies = [
 
 [[package]]
 name = "pyo3-macros-backend"
-version = "0.23.5"
+version = "0.25.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fca6726ad0f3da9c9de093d6f116a93c1a38e417ed73bf138472cf4064f72028"
+checksum = "4109984c22491085343c05b0dbc54ddc405c3cf7b4374fc533f5c3313a572ccc"
 dependencies = [
  "heck",
  "proc-macro2",
@@ -3530,9 +3529,9 @@ checksum = "7b2093cf4c8eb1e67749a6762251bc9cd836b6fc171623bd0a9d324d37af2417"
 
 [[package]]
 name = "target-lexicon"
-version = "0.12.16"
+version = "0.13.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "61c41af27dd6d1e27b1b16b489db798443478cef1f06a660c96db617ba5de3b1"
+checksum = "adb6935a6f5c20170eeceb1a3835a49e12e19d792f6dd344ccc76a985ca5a6ca"
 
 [[package]]
 name = "tempfile"
diff --git a/README.md b/README.md
index 71b5855..d372060 100644
--- a/README.md
+++ b/README.md
@@ -119,7 +119,16 @@ Opsqueue's client libraries and binary itself are also available through `niv`.
 2. Package the now available `opsqueue` library as part of your overlay, using e.g.
 
 ```nix
-opsqueue = self.callPackage (sources.opsqueue + "/libs/opsqueue_python/opsqueue_python.nix") { };
+opsqueue_client = self.callPackage (sources.opsqueue + "/libs/opsqueue_python/opsqueue_python.nix") { };
+```
+
+- If you want to override which Rust version is used, you can set the `rustToolchain` either in an overlay or by passing it as parameter directly to `callPackage`.
+- If you want to override which Python version is used for the Python client, you can set `python` either in an overlay or by passing it as parameter directly to `callPackage`.
+
+For example:
+
+```nix
+opsqueue_client = self.callPackage (sources.opsqueue + "/libs/opsqueue_python/opsqueue_python.nix") { python = mySpecialPython; };
 ```
 
 ## For devs modifying Opsqueue: Building, running, testing
diff --git a/libs/opsqueue_python/Cargo.toml b/libs/opsqueue_python/Cargo.toml
index ae28c39..a1f8e86 100644
--- a/libs/opsqueue_python/Cargo.toml
+++ b/libs/opsqueue_python/Cargo.toml
@@ -30,10 +30,10 @@ anyhow = "1.0.86"
 thiserror = "1.0.65"
 
 # Python FFI:
-pyo3 = { version = "0.23.4", features = ["chrono"] }
-pyo3-async-runtimes = { version = "0.23.0", features = ["tokio-runtime", "unstable-streams"] }
+pyo3 = { version = "0.25", features = ["chrono"] }
+pyo3-async-runtimes = { version = "0.25", features = ["tokio-runtime", "unstable-streams"] }
 once_cell = "1.21.3" # Only currently used for `unsync::OnceCell` as part of PyO3 async helpers.
 
 # Logging/tracing:
-pyo3-log = "0.12.1"
+pyo3-log = "0.12"
 tracing = { version = "0.1.41", features = ["log"] }
diff --git a/libs/opsqueue_python/opsqueue_python.nix b/libs/opsqueue_python/opsqueue_python.nix
index 19e1365..079c3da 100644
--- a/libs/opsqueue_python/opsqueue_python.nix
+++ b/libs/opsqueue_python/opsqueue_python.nix
@@ -23,9 +23,12 @@
   opentelemetry-api,
   opentelemetry-exporter-otlp,
   opentelemetry-sdk,
+
+  # Downstream users can override which precise Python version is used.
+  # This is opt-in; by default we will use whatever 'python3' is in scope.
+  python ? (pkgs.python3),
 }:
 let
-  python = pkgs.python3;
   sources = import ../../nix/sources.nix;
   crane = import sources.crane { pkgs = pkgs; };
   craneLib = crane.overrideToolchain (pkgs: rustToolchain);