diff --git a/CHANGELOG.md b/CHANGELOG.md
index b093b58..e0836b1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,10 @@ Version numbers follow [Semantic Versioning](https://semver.org/spec/v2.0.0.html
 
 ## [Unreleased]
 
+---
+
+## [0.3.4] — 2026-08-12
+
 ### Changed
 
 - Dependency floors raised across the board by the Dependabot batch of
@@ -29,6 +33,10 @@ Version numbers follow [Semantic Versioning](https://semver.org/spec/v2.0.0.html
   environment installed before this batch may sit below the declared floor —
   re-run `pip install -e ".[dev]"`.
 
+- `pyproject.toml`: `license` is now the canonical SPDX expression
+  `GPL-3.0-only` instead of the deprecated `GPL-3.0` identifier. The license
+  itself is unchanged — only its machine-readable spelling.
+
 ---
 
 ## [0.3.3] — 2026-07-14
@@ -501,7 +509,8 @@ Version numbers follow [Semantic Versioning](https://semver.org/spec/v2.0.0.html
 
 ---
 
-[Unreleased]: https://github.com/NC3-TestingPlatform/mailvalidator/compare/v0.3.3...HEAD
+[Unreleased]: https://github.com/NC3-TestingPlatform/mailvalidator/compare/v0.3.4...HEAD
+[0.3.4]: https://github.com/NC3-TestingPlatform/mailvalidator/compare/v0.3.3...v0.3.4
 [0.3.3]: https://github.com/NC3-TestingPlatform/mailvalidator/compare/v0.3.2...v0.3.3
 [0.3.2]: https://github.com/NC3-TestingPlatform/mailvalidator/compare/v0.3.1...v0.3.2
 [0.3.1]: https://github.com/NC3-TestingPlatform/mailvalidator/compare/v0.3.0...v0.3.1
diff --git a/mailvalidator/__init__.py b/mailvalidator/__init__.py
index 2b0b7df..60d6da7 100644
--- a/mailvalidator/__init__.py
+++ b/mailvalidator/__init__.py
@@ -5,7 +5,7 @@
 try:
     __version__ = version("mailvalidator")
 except PackageNotFoundError:  # pragma: no cover – only when package not installed
-    __version__ = "0.3.3"
+    __version__ = "0.3.4"
 
 # NullHandler so library users who have not configured logging
 # do not see "No handler found" warnings (PEP 3118 / logging HOWTO).
diff --git a/pyproject.toml b/pyproject.toml
index 6046a6c..2d53eec 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,11 +4,11 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "mailvalidator"
-version = "0.3.3"
+version = "0.3.4"
 description = "Mail server configuration assessment CLI utility"
 readme = "README.md"
 requires-python = ">=3.11"
-license = "GPL-3.0"
+license = "GPL-3.0-only"
 license-files = ["LICENSE"]
 authors = [{ name = "t0kubetsu" }]
 keywords = [