tomschr · Sep 26, 2026 · Sep 26, 2026 · Sep 26, 2026
diff --git a/changelog.d/pr486.bugfix.rst b/changelog.d/pr486.bugfix.rst
@@ -0,0 +1 @@
+Fix :meth:`~semver.Version.next_version` to drop the build metadata when incrementing an old-style prerelease without a dot separator (for example ``rc3``). Previously ``1.2.3-rc3+build.5`` became ``1.2.3-rc4+build.5`` while ``1.2.3-rc.3+build.5`` became ``1.2.3-rc.4``.
diff --git a/src/semver/version.py b/src/semver/version.py
@@ -544,7 +544,9 @@ def next_version(self, part: str, prerelease_token: str = "rc") -> "Version":
                 match = re.match(f"^{prerelease_token}(\\d+)$", version.prerelease)
                 if match:
                     num = int(match.group(1))
-                    return version.replace(prerelease=f"{prerelease_token}{num + 1}")
+                    return version.replace(
+                        prerelease=f"{prerelease_token}{num + 1}", build=None
+                    )
 
                 current_token = version.prerelease.split(".")[0]
                 if current_token != prerelease_token:

diff --git a/tests/test_issue484.py b/tests/test_issue484.py
@@ -31,3 +31,9 @@ def test_issue_484_custom_token():
     """Custom prerelease token should be respected."""
     v = Version.parse("1.2.3-beta2")
     assert str(v.next_version("prerelease", "beta")) == "1.2.3-beta3"
+
+
+def test_issue_484_old_style_drops_build():
+    """Build metadata is dropped, as it is for dot-separated prereleases."""
+    v = Version.parse("1.2.3-rc3+build.5")
+    assert v.next_version("prerelease").build is None
diff --git a/tests/test_parsing.py b/tests/test_parsing.py
@@ -208,6 +208,7 @@ def test_next_version_with_invalid_parts():
         # prerelease+build: build is stripped along with prerelease during finalization
         ("1.2.3-rc.1+build.5", "patch", "1.2.3"),
         ("1.2.3-rc.1+build.5", "prerelease", "1.2.3-rc.2"),
+        ("1.2.3-rc1+build.5", "prerelease", "1.2.3-rc2"),
     ],
 )
 def test_next_version_with_versioninfo(version, part, expected):
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Fix :meth:`~semver.Version.next_version` to drop the build metadata when incrementing an old-style prerelease without a dot separator (for example ``rc3``). Previously ``1.2.3-rc3+build.5`` became ``1.2.3-rc4+build.5`` while ``1.2.3-rc.3+build.5`` became ``1.2.3-rc.4``.