diff --git a/Cargo.lock b/Cargo.lock
index f6bdf025..6b41da97 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -91,24 +91,24 @@ checksum = "3094308123a0e9fd59659ce45e22de9f53fc1d2ac6e1feb9fef988e4f76cad77"
 
 [[package]]
 name = "instant"
-version = "0.1.10"
+version = "0.1.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bee0328b1209d157ef001c94dd85b4f8f64139adb0eac2659f4b08382b2f474d"
+checksum = "716d3d89f35ac6a34fd0eed635395f4c3b76fa889338a4632e5231a8684216bd"
 dependencies = [
  "cfg-if 1.0.0",
 ]
 
 [[package]]
 name = "itoa"
-version = "0.4.7"
+version = "0.4.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dd25036021b0de88a0aff6b850051563c6516d0bf53f8638938edbb9de732736"
+checksum = "b71991ff56294aa922b450139ee08b3bfc70982c6b2c7562771375cf73542dd4"
 
 [[package]]
 name = "libc"
-version = "0.2.99"
+version = "0.2.103"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a7f823d141fe0a24df1e23b4af4e3c7ba9e5966ec514ea068c93024aa7deb765"
+checksum = "dd8f7255a17a627354f321ef0055d63b898c6fb27eff628af4d1b66b7331edf6"
 
 [[package]]
 name = "libm"
@@ -118,9 +118,9 @@ checksum = "7fc7aa29613bd6a620df431842069224d8bc9011086b1db4c0e0cd47fa03ec9a"
 
 [[package]]
 name = "lock_api"
-version = "0.4.4"
+version = "0.4.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0382880606dff6d15c9476c416d18690b72742aa7b605bb6dd6ec9030fbf07eb"
+checksum = "712a4d093c9976e24e7dbca41db895dabcbac38eb5f4045393d17a95bdfb1109"
 dependencies = [
  "scopeguard",
 ]
@@ -172,9 +172,9 @@ dependencies = [
 
 [[package]]
 name = "packed_simd_2"
-version = "0.3.5"
+version = "0.3.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0e64858a2d3733fdd61adfdd6da89aa202f7ff0e741d2fc7ed1e452ba9dc99d7"
+checksum = "71c0c06716cfc81616fa8e22b721ce92fecd594508bc0eb3d04ae3ef35ac10c5"
 dependencies = [
  "cfg-if 0.1.10",
  "libm",
@@ -182,9 +182,9 @@ dependencies = [
 
 [[package]]
 name = "parking_lot"
-version = "0.11.1"
+version = "0.11.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6d7744ac029df22dca6284efe4e898991d28e3085c706c972bcd7da4a27a15eb"
+checksum = "7d17b78036a60663b797adeaee46f5c9dfebb86948d1255007a1d6be0271ff99"
 dependencies = [
  "instant",
  "lock_api",
@@ -193,9 +193,9 @@ dependencies = [
 
 [[package]]
 name = "parking_lot_core"
-version = "0.8.3"
+version = "0.8.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fa7a782938e745763fe6907fc6ba86946d72f49fe7e21de074e08128a99fb018"
+checksum = "d76e8e1493bcac0d2766c42737f34458f1c8c50c0d23bcb24ea953affb273216"
 dependencies = [
  "cfg-if 1.0.0",
  "instant",
@@ -207,9 +207,9 @@ dependencies = [
 
 [[package]]
 name = "pyo3"
-version = "0.14.2"
+version = "0.14.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "af205762ba65eec9f27a2fa1a57a40644e8e3368784b8c8b2f2de48f6e8ddd96"
+checksum = "35100f9347670a566a67aa623369293703322bb9db77d99d7df7313b575ae0c8"
 dependencies = [
  "cfg-if 1.0.0",
  "libc",
@@ -219,9 +219,9 @@ dependencies = [
 
 [[package]]
 name = "pyo3-build-config"
-version = "0.14.2"
+version = "0.14.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "755944027ce803c7238e59c5a18e59c1d0a4553db50b23e9ba209a568353028d"
+checksum = "d12961738cacbd7f91b7c43bc25cfeeaa2698ad07a04b3be0aa88b950865738f"
 dependencies = [
  "once_cell",
 ]
@@ -249,15 +249,15 @@ checksum = "d29ab0c6d3fc0ee92fe66e2d99f700eab17a8d57d1c1d3b748380fb20baa78cd"
 
 [[package]]
 name = "serde"
-version = "1.0.127"
+version = "1.0.130"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f03b9878abf6d14e6779d3f24f07b2cfa90352cfec4acc5aab8f1ac7f146fae8"
+checksum = "f12d06de37cf59146fbdecab66aa99f9fe4f78722e3607577a5375d66bd0c913"
 
 [[package]]
 name = "serde_json"
-version = "1.0.66"
+version = "1.0.68"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "336b10da19a12ad094b59d870ebde26a45402e5b470add4b5fd03c5048a32127"
+checksum = "0f690853975602e1bfe1ccbf50504d67174e3bcf340f23b5ea9992e0587a52d8"
 dependencies = [
  "itoa",
  "ryu",
@@ -272,9 +272,9 @@ checksum = "c970da16e7c682fa90a261cf0724dee241c9f7831635ecc4e988ae8f3b505559"
 
 [[package]]
 name = "smallvec"
-version = "1.6.1"
+version = "1.7.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fe0f37c9e8f3c5a4a66ad655a93c74daac4ad00c441533bf5c6e7990bb42604e"
+checksum = "1ecab6c735a6bb4139c0caafd0cc3635748bbb3acf4550e8138122099251f309"
 
 [[package]]
 name = "version_check"
diff --git a/Cargo.toml b/Cargo.toml
index 9af15bb8..dc0e847a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -69,12 +69,12 @@ encoding_rs = { version = "0.8", default_features = false }
 inlinable_string = { version = "0.1" }
 itoa = { version = "0.4", default_features = false }
 once_cell = { version = "1", default_features = false }
-pyo3 = { version = "^0.14.2", default_features = false, features = ["extension-module"]}
+pyo3 = { version = "^0.14.5", default_features = false, features = ["extension-module"]}
 ryu = { version = "1", default_features = false }
 serde = { version = "1", default_features = false }
-serde_json = { version = "^1.0.66", default_features = false, features = ["std", "float_roundtrip"] }
+serde_json = { version = "^1.0.68", default_features = false, features = ["std", "float_roundtrip"] }
 simdutf8 = { version = "0.1", default_features = false, features = ["std"] }
-smallvec = { version = "^1.6", default_features = false, features = ["union", "write"] }
+smallvec = { version = "^1.7", default_features = false, features = ["union", "write"] }
 
 [profile.release]
 codegen-units = 1
@@ -83,3 +83,6 @@ incremental = false
 lto = "thin"
 opt-level = 3
 panic = "abort"
+
+[profile.release.build-override]
+opt-level = 0
diff --git a/README.md b/README.md
index 831354db..eec7eb2a 100644
--- a/README.md
+++ b/README.md
@@ -1171,7 +1171,7 @@ maturin build --no-sdist --release --strip --cargo-extra-args="--features=unstab
 
 To build on the stable channel, do not specify `--features=unstable-simd`.
 
-The project's own CI tests against `nightly-2021-08-17` and stable 1.54. It
+The project's own CI tests against `nightly-2021-10-01` and stable 1.54. It
 is prudent to pin the nightly version because that channel can introduce
 breaking changes.
 
diff --git a/build.rs b/build.rs
new file mode 100644
index 00000000..5ac15b5a
--- /dev/null
+++ b/build.rs
@@ -0,0 +1,13 @@
+use std::process::Command;
+
+fn main() {
+    let out = Command::new("python")
+        .args(&["-c", "import sys; print(sys.version_info[1])"])
+        .output()
+        .expect("python version did not print");
+    let version = u8::from_str_radix(String::from_utf8_lossy(&out.stdout).trim(), 10)
+        .expect("python version was not parsed");
+    for each in 8..(version + 1) {
+        println!("cargo:rustc-cfg=Py_3_{}", each);
+    }
+}
diff --git a/ci/azure-debug.yml b/ci/azure-debug.yml
index 2b2fbf52..e259a76b 100644
--- a/ci/azure-debug.yml
+++ b/ci/azure-debug.yml
@@ -20,7 +20,7 @@ steps:
   displayName: rustup
 - bash: PATH=$(path) rustup default $(toolchain)
   displayName: ensure toolchain
-- bash: PATH=$(path) $(interpreter) -m pip install --user --upgrade pip maturin==0.11.2
+- bash: PATH=$(path) $(interpreter) -m pip install --user --upgrade pip maturin==0.11.4
   displayName: build dependencies
 - bash: PATH=$(path) $(interpreter) -m pip install --user -r test/requirements.txt -r integration/requirements.txt
   displayName: test dependencies
diff --git a/ci/azure-linux-container.yml b/ci/azure-linux-container.yml
index 276c916b..a7f7cf21 100644
--- a/ci/azure-linux-container.yml
+++ b/ci/azure-linux-container.yml
@@ -20,7 +20,7 @@ steps:
   displayName: rustup
 - bash: PATH=$(path) rustup default $(toolchain)
   displayName: ensure toolchain
-- bash: PATH=$(path) $(interpreter) -m pip install --user --upgrade pip maturin==0.11.2 auditwheel
+- bash: PATH=$(path) $(interpreter) -m pip install --user --upgrade pip maturin==0.11.4 auditwheel
   displayName: build dependencies
 - bash: PATH=$(path) maturin build --no-sdist --release --strip $(extra) --compatibility $(manylinux) --interpreter $(interpreter)
   env:
diff --git a/ci/azure-macos.yml b/ci/azure-macos.yml
index 75f7d3db..ed8cd365 100644
--- a/ci/azure-macos.yml
+++ b/ci/azure-macos.yml
@@ -7,7 +7,7 @@ steps:
   displayName: rustup
 - bash: rustup default $(toolchain)
   displayName: ensure toolchain
-- bash: pip install --upgrade pip maturin==0.11.2
+- bash: pip install --upgrade pip maturin==0.11.4
   displayName: build dependencies
 - bash: pip install -r test/requirements.txt -r integration/requirements.txt
   displayName: test dependencies
diff --git a/ci/azure-pipelines.yml b/ci/azure-pipelines.yml
index 4dce739a..ed9b3e1f 100644
--- a/ci/azure-pipelines.yml
+++ b/ci/azure-pipelines.yml
@@ -4,7 +4,7 @@ pr:
     - '*'
 
 variables:
-  toolchain: nightly-2021-08-17
+  toolchain: nightly-2021-10-01
 
 jobs:
 
@@ -180,7 +180,7 @@ jobs:
   pool:
     vmImage: windows-2019
   variables:
-    interpreter: C:\hostedtoolcache\windows\Python\3.9.6\x64\python.exe
+    interpreter: C:\hostedtoolcache\windows\Python\3.9.7\x64\python.exe
     target: x86_64-pc-windows-msvc
   steps:
   - task: UsePythonVersion@0
diff --git a/ci/azure-sdist.yml b/ci/azure-sdist.yml
index 29790e23..1cf9cd9c 100644
--- a/ci/azure-sdist.yml
+++ b/ci/azure-sdist.yml
@@ -14,7 +14,7 @@ steps:
   displayName: rustup
 - bash: PATH=$(path) rustup default $(toolchain)
   displayName: ensure toolchain
-- bash: PATH=$(path) $(interpreter) -m pip install --user --upgrade pip maturin==0.11.2
+- bash: PATH=$(path) $(interpreter) -m pip install --user --upgrade pip maturin==0.11.4
   displayName: build dependencies
 - bash: PATH=$(path) $(interpreter) -m pip install --user -r test/requirements.txt -r integration/requirements.txt
   displayName: test dependencies
diff --git a/ci/azure-win.yml b/ci/azure-win.yml
index 4d0620dd..76d9717a 100644
--- a/ci/azure-win.yml
+++ b/ci/azure-win.yml
@@ -11,7 +11,7 @@ steps:
     rustup default $(toolchain)
     echo "##vso[task.setvariable variable=PATH;]%PATH%;%USERPROFILE%\.cargo\bin"
   displayName: rustup
-- script: python.exe -m pip install --upgrade pip maturin==0.11.2
+- script: python.exe -m pip install --upgrade pip maturin==0.11.4
   displayName: build dependencies
 - script: python.exe -m pip install -r test\requirements.txt -r integration\requirements.txt
   displayName: test dependencies
diff --git a/ci/drone.yml b/ci/drone.yml
index 3a724cfa..f3225522 100644
--- a/ci/drone.yml
+++ b/ci/drone.yml
@@ -14,8 +14,8 @@ steps:
     MATURIN_PASSWORD:
       from_secret: twine_password
   commands:
-    - curl https://sh.rustup.rs -sSf | sh -s -- --default-toolchain nightly-2021-08-17 --profile minimal -y
-    - python3.10 -m pip install --user --upgrade pip maturin==0.11.2
+    - curl https://sh.rustup.rs -sSf | sh -s -- --default-toolchain nightly-2021-10-01 --profile minimal -y
+    - python3.10 -m pip install --user --upgrade pip maturin==0.11.4
     - maturin build --no-sdist --release --strip --compatibility 2_24 --cargo-extra-args="--features=unstable-simd" --interpreter python3.10
     - python3.10 -m pip install --user target/wheels/orjson*.whl
     - python3.10 -m pip install --user -r test/requirements.txt -r integration/requirements.txt
@@ -38,8 +38,8 @@ steps:
     MATURIN_PASSWORD:
       from_secret: twine_password
   commands:
-    - curl https://sh.rustup.rs -sSf | sh -s -- --default-toolchain nightly-2021-08-17 --profile minimal -y
-    - python3.9 -m pip install --user --upgrade pip maturin==0.11.2
+    - curl https://sh.rustup.rs -sSf | sh -s -- --default-toolchain nightly-2021-10-01 --profile minimal -y
+    - python3.9 -m pip install --user --upgrade pip maturin==0.11.4
     - maturin build --no-sdist --release --strip --compatibility 2_24 --cargo-extra-args="--features=unstable-simd" --interpreter python3.9
     - python3.9 -m pip install --user target/wheels/orjson*.whl
     - python3.9 -m pip install --user -r test/requirements.txt -r integration/requirements.txt
@@ -62,8 +62,8 @@ steps:
     MATURIN_PASSWORD:
       from_secret: twine_password
   commands:
-    - curl https://sh.rustup.rs -sSf | sh -s -- --default-toolchain nightly-2021-08-17 --profile minimal -y
-    - python3.8 -m pip install --user --upgrade pip maturin==0.11.2
+    - curl https://sh.rustup.rs -sSf | sh -s -- --default-toolchain nightly-2021-10-01 --profile minimal -y
+    - python3.8 -m pip install --user --upgrade pip maturin==0.11.4
     - maturin build --no-sdist --release --strip --compatibility 2_24 --cargo-extra-args="--features=unstable-simd" --interpreter python3.8
     - python3.8 -m pip install --user target/wheels/orjson*.whl
     - python3.8 -m pip install --user -r test/requirements.txt -r integration/requirements.txt
@@ -86,8 +86,8 @@ steps:
     MATURIN_PASSWORD:
       from_secret: twine_password
   commands:
-    - curl https://sh.rustup.rs -sSf | sh -s -- --default-toolchain nightly-2021-08-17 --profile minimal -y
-    - python3.7 -m pip install --user --upgrade pip maturin==0.11.2
+    - curl https://sh.rustup.rs -sSf | sh -s -- --default-toolchain nightly-2021-10-01 --profile minimal -y
+    - python3.7 -m pip install --user --upgrade pip maturin==0.11.4
     - maturin build --no-sdist --release --strip --compatibility 2_24 --cargo-extra-args="--features=unstable-simd" --interpreter python3.7
     - python3.7 -m pip install --user target/wheels/orjson*.whl
     - python3.7 -m pip install --user -r test/requirements.txt -r integration/requirements.txt
diff --git a/pyproject.toml b/pyproject.toml
index 3d061173..ae4a1139 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ repository = "https://github.com/ijl/orjson"
 
 [build-system]
 build-backend = "maturin"
-requires = ["maturin>=0.11.2,<0.12"]
+requires = ["maturin>=0.11.4,<0.12"]
 
 [tool.maturin]
 sdist-include = ["Cargo.lock"]
@@ -12,5 +12,5 @@ strip = true
 
 [tool.black]
 line-length = 88
-target-version = ['py36', 'py37', 'py38']
+target-version = ['py37', 'py38', 'py39']
 include = '\.pyi?$'
diff --git a/test/test_transform.py b/test/test_transform.py
index eab7848d..f39d9fa3 100644
--- a/test/test_transform.py
+++ b/test/test_transform.py
@@ -83,7 +83,7 @@ def test_object_same_key_unclear_values(self):
         """
         object_same_key_unclear_values.json
         """
-        self._pass_transform("object_same_key_unclear_values.json", b'{"a":0}')
+        self._pass_transform("object_same_key_unclear_values.json", b'{"a":-0.0}')
 
     def test_string_1_escaped_invalid_codepoint(self):
         """