@@ -0,0 +1,4 @@
+Allow empty string or ``None``` as token in
+:meth:`Version.bump_build <semver.Version.bump_build>` and
+:meth:`Version.bump_prerelease <semver.Version.bump_prerelease>`.
+
@@ -1,3 +1,4 @@
+.. _increase-parts-of-a-version:
 Increasing Parts of a Version Taking into Account Prereleases
 =============================================================
 
 
@@ -1,6 +1,19 @@
 Raising Parts of a Version
 ==========================
 
+.. note::
+
+   Keep in mind, "raising" the pre-release only will make your
+   complete version *lower* than before.
+
+   For example, having version ``1.0.0`` and raising the pre-release
+   will lead to ``1.0.0-rc.1``, but ``1.0.0-rc.1`` is smaller than ``1.0.0``.
+
+   If you search for a way to take into account this behavior, look for the
+   method :meth:`Version.next_version <semver.version.Version.next_version>`
+   in section :ref:`increase-parts-of-a-version`.
+
+
 The ``semver`` module contains the following functions to raise parts of
 a version:
 
@@ -14,6 +27,7 @@ a version:
   ``build`` to ``None``.
 * :func:`Version.bump_build <semver.version.Version.bump_build>`: raises the build part.
 
+
 .. code-block:: python
 
     >>> str(Version.parse("3.4.5-pre.2+build.4").bump_major())
@@ -29,7 +43,7 @@ a version:
 
 Likewise the module level functions :func:`semver.bump_major`.
 
-For the functions :func:`Version.bump_prerelease <semver.version.Version.bump_prerelease>` and :func:`Version.bump_build <semver.version.Version.bump_build>` it's possible to pass an empty string or ``None``. However,
+For the methods :func:`Version.bump_prerelease <semver.version.Version.bump_prerelease>` and :func:`Version.bump_build <semver.version.Version.bump_build>` it's possible to pass an empty string or ``None``. However,
 it gives different results::
 
 .. code-block:: python
 
@@ -319,6 +319,8 @@ def bump_prerelease(self, token: Optional[str] = "rc") -> "Version":
         'rc.2'
         >>> ver.bump_prerelease('').prerelease
         '1'
+        >>> ver.bump_prerelease(None).prerelease
+        'rc.1'
         """
         cls = type(self)
         if self._prerelease is not None:
@@ -330,11 +332,9 @@ def bump_prerelease(self, token: Optional[str] = "rc") -> "Version":
         else:
             prerelease = str(token) + ".0"
 
-        # self._prerelease or (token or "rc") + ".0"
         prerelease = cls._increment_string(prerelease)
         return cls(self._major, self._minor, self._patch, prerelease)
 
-    # VersionPart = Union[int, Optional[str]]
     def bump_build(self, token: Optional[str] = "build") -> "Version":
         """
         Raise the build part of the version, return a new object but leave self
@@ -359,6 +359,17 @@ def bump_build(self, token: Optional[str] = "build") -> "Version":
         else:
             build = str(token) + ".0"
 
+        # self._build or (token or "build") + ".0"
+        build = cls._increment_string(build)
+        if self._build is not None:
+            build = self._build
+        elif token == "":
+            build = "0"
+        elif token is None:
+            build = "build.0"
+        else:
+            build = str(token) + ".0"
+
         # self._build or (token or "build") + ".0"
         build = cls._increment_string(build)
         return cls(self._major, self._minor, self._patch, self._prerelease, build)
Original file line number	Diff line number	Diff line change
`@@ -1,3 +1,4 @@`
	`1`	`+.. _increase-parts-of-a-version:`
`1`	`2`	`Increasing Parts of a Version Taking into Account Prereleases`
`2`	`3`	`=============================================================`
`3`	`4`