diff --git a/.flake8 b/.flake8
index aa447ff..26beb5f 100644
--- a/.flake8
+++ b/.flake8
@@ -18,8 +18,6 @@
 #       E704 multiple statements on one line (def) -- disallows function body on the same line as the def
 #
 # flake8-bugbear rules that cause too many false positives:
-#       B905 "`zip()` without an explicit `strict=True` parameter --
-#           the `strict` parameter was introduced in Python 3.10; we support Python 3.9
 #       B907 "Use !r inside f-strings instead of manual quotes" --
 #           produces false positives if you're surrounding things with double quotes
 
@@ -29,5 +27,5 @@ max-line-length = 80
 max-complexity = 12
 noqa-require-code = true
 per-file-ignores =
-  *.py: B905, B907, B950, E203, E501, W503, W291, W293
+  *.py: B907, B950, E203, E501, W503, W291, W293
   *.pyi: B, E301, E302, E305, E501, E701, E704, F821, W503
diff --git a/.github/workflows/check.yml b/.github/workflows/check.yml
index 94c8c56..41096a0 100644
--- a/.github/workflows/check.yml
+++ b/.github/workflows/check.yml
@@ -29,13 +29,13 @@ jobs:
     timeout-minutes: 5
     strategy:
       matrix:
-        python-version: ["3.9", "3.14"]
+        python-version: ["3.10", "3.14"]
       fail-fast: false
     steps:
       - uses: actions/checkout@v4
       - uses: astral-sh/setup-uv@v6
       - run: |
-          uv run --python=3.13 --group=dev mypy --python-version=${{ matrix.python-version }}
+          uv run --python=3.14 --group=dev mypy --python-version=${{ matrix.python-version }}
 
   flake8:
     name: flake8
@@ -45,7 +45,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: astral-sh/setup-uv@v6
       - run: |
-          uv run --python=3.13 --group=dev flake8 $(git ls-files | grep 'py$') --color=always
+          uv run --python=3.14 --group=dev flake8 $(git ls-files | grep 'py$') --color=always
 
   tests:
     name: pytest suite
@@ -54,7 +54,7 @@ jobs:
     strategy:
       matrix:
         os: ["ubuntu-latest", "macos-latest", "windows-latest"]
-        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13", "3.14"]
+        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14"]
       fail-fast: false
     steps:
       - uses: actions/checkout@v4
diff --git a/.github/workflows/typeshed_primer.yml b/.github/workflows/typeshed_primer.yml
index be56599..5e6e0df 100644
--- a/.github/workflows/typeshed_primer.yml
+++ b/.github/workflows/typeshed_primer.yml
@@ -39,7 +39,7 @@ jobs:
       - name: Setup Python
         uses: actions/setup-python@v5
         with:
-          python-version: "3.13"
+          python-version: "3.14"
       - name: Install uv
         run: curl -LsSf https://astral.sh/uv/install.sh | sh
       - run: uv pip install flake8-noqa --system
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 08cd7cd..cab692d 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -12,11 +12,11 @@ repos:
       - id: name-tests-test
         args: [--pytest-test-first]
   - repo: https://github.com/psf/black-pre-commit-mirror
-    rev: 25.11.0 # must match pyproject.toml
+    rev: 25.12.0 # must match pyproject.toml
     hooks:
       - id: black
   - repo: https://github.com/pycqa/isort
-    rev: 6.1.0 # must match pyproject.toml
+    rev: 7.0.0 # must match pyproject.toml
     hooks:
       - id: isort
         name: isort (python)
diff --git a/CHANGELOG.md b/CHANGELOG.md
index af8d8b0..0303ad0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -15,6 +15,10 @@ flake8-pyi uses Calendar Versioning (CalVer).
 
 * Y068: Don't use `@override` in stub files
 
+### Other changes
+
+* Drop support for Python 3.9
+
 ## 25.5.0
 
 ### New Error Codes
diff --git a/flake8_pyi/visitor.py b/flake8_pyi/visitor.py
index 4bb1cb6..35d6329 100644
--- a/flake8_pyi/visitor.py
+++ b/flake8_pyi/visitor.py
@@ -2114,8 +2114,7 @@ def visit_arg(self, node: ast.arg) -> None:
     def visit_arguments(self, node: ast.arguments) -> None:
         args = node.posonlyargs + node.args
         defaults = [None] * (len(args) - len(node.defaults)) + node.defaults
-        assert len(args) == len(defaults)
-        for arg, default in zip(args, defaults):
+        for arg, default in zip(args, defaults, strict=True):
             self.check_arg_default(arg, default)
         if node.vararg is not None:
             self.visit(node.vararg)
diff --git a/pyproject.toml b/pyproject.toml
index 343ed9e..7b85612 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -18,7 +18,7 @@ maintainers = [
 description = "A plugin for flake8 to enable linting .pyi stub files."
 license = "MIT"
 readme = "README.md"
-requires-python = ">=3.9"
+requires-python = ">=3.10"
 keywords = [
     "flake8",
     "pyi",
@@ -37,7 +37,6 @@ classifiers = [
     "Operating System :: OS Independent",
     "Programming Language :: Python",
     "Programming Language :: Python :: 3 :: Only",
-    "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
@@ -53,10 +52,10 @@ dependencies = [
 
 [dependency-groups]
 dev = [
-    "black==25.11.0",            # Must match .pre-commit-config.yaml
+    "black==25.12.0",            # Must match .pre-commit-config.yaml
     "flake8-bugbear==24.12.12",
     "flake8-noqa==1.4.0",
-    "isort==6.1.0",             # Must match .pre-commit-config.yaml
+    "isort==7.0.0",             # Must match .pre-commit-config.yaml
     "mypy==1.15.0",
     "pre-commit-hooks==5.0.0",  # Must match .pre-commit-config.yaml
     "pytest==8.3.5",
@@ -86,7 +85,7 @@ skip = ["tests/imports.pyi", "tests/pep604_union_types.pyi"]
 skip_gitignore = true
 
 [tool.black]
-target-version = ['py39']
+target-version = ['py310']
 skip-magic-trailing-comma = true
 force-exclude = ".*\\.pyi"