diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1d5612e..bb32b89 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
+## [0.3.1] - 2024-07-03
+
+### Fixed
+
+- Missing sub-packages problem when installing with pip from the repo; Fix for Issue https://github.com/blakeaw/pysb-pkpd/issues/16
+
 ## [0.3.0] - 2024-07-01
 
 ### Added
diff --git a/README.md b/README.md
index f4b3afb..01fe9ea 100644
--- a/README.md
+++ b/README.md
@@ -3,8 +3,8 @@
 ![Python version badge](https://img.shields.io/badge/python-3.11.3-blue.svg)
 [![PySB version badge](https://img.shields.io/badge/PySB->%3D1.15.0-9cf.svg)](https://pysb.org/)
 [![license](https://img.shields.io/github/license/blakeaw/pysb-pkpd.svg)](LICENSE)
-![version](https://img.shields.io/badge/version-0.3.0-orange.svg)
-[![release](https://img.shields.io/github/release-pre/blakeaw/pysb-pkpd.svg)](https://github.com/blakeaw/pysb-pkpd/releases/tag/v0.3.0)
+![version](https://img.shields.io/badge/version-0.3.1-orange.svg)
+[![release](https://img.shields.io/github/release-pre/blakeaw/pysb-pkpd.svg)](https://github.com/blakeaw/pysb-pkpd/releases/tag/v0.3.1)
 
 
 __`pysb-pkpd` enables you to efficiently program and simulate dynamic PK/PD and QSP models in Python using the PySB modeling framework.__ 
@@ -56,27 +56,27 @@ Note that `pysb-pkpd` has the following core dependencies:
 
 ### pip install
 
-You can install `pysb-pkpd` version 0.3.0 with `pip` sourced from the GitHub repo:
+You can install `pysb-pkpd` version 0.3.1 with `pip` sourced from the GitHub repo:
 
 ##### with git installed:
 
 Fresh install:
 ```
-pip install git+https://github.com/blakeaw/pysb-pkpd@v0.3.0
+pip install git+https://github.com/blakeaw/pysb-pkpd@v0.3.1
 ```
 Or to upgrade from an older version:
 ```
-pip install --upgrade git+https://github.com/blakeaw/pysb-pkpd@v0.3.0
+pip install --upgrade git+https://github.com/blakeaw/pysb-pkpd@v0.3.1
 ```
 ##### without git installed:
 
 Fresh install:
 ```
-pip install https://github.com/blakeaw/pysb-pkpd/archive/refs/tags/v0.3.0.zip
+pip install https://github.com/blakeaw/pysb-pkpd/archive/refs/tags/v0.3.1.zip
 ```
 Or to upgrade from an older version:
 ```
-pip install --upgrade https://github.com/blakeaw/pysb-pkpd/archive/refs/tags/v0.3.0.zip
+pip install --upgrade https://github.com/blakeaw/pysb-pkpd/archive/refs/tags/v0.3.1.zip
 ```
 ### Manual install
 
@@ -246,7 +246,9 @@ I'm very happy that you've chosen to use __pysb-pkpd__. This add-on is a project
 * **Star** :star: : Show your support by starring the [pysb-pkpd GitHub repository](https://github.com/blakeaw/pysb-pkpd). It helps increase the project's visibility and lets others know it's useful. It also benefits my motivation to continue improving the package!
 * **Share** :mega: : Sharing `pysb-pkpd` on your social media, forums, or with your network is another great way to support the project. It helps more people discover `pysb-pkpd`, which in turn motivates me to keep developing!
 * **Cite** :books: : Citing or mentioning this software in your work, publications, or projects is another valuable way to support it. It helps spread the word and acknowledges the effort put into its development, which is greatly appreciated!
-* **Sponsor** :dollar: : Even small contributions through my Ko-fi page, [ko-fi.com/blakeaw](https://ko-fi.com/blakeaw), can make a big difference. Every little bit can help me continue developing this and other open-source projects, and I truly appreciate your support!
+* **Sponsor** :dollar: : Even small financial contributions, such as spotting me the cost of a tea through Ko-fi so I can get my caffeine fix, can make a big difference! Every little bit can help me continue developing this and other open-source projects. 
+
+[![ko-fi](https://ko-fi.com/img/githubbutton_sm.svg)](https://ko-fi.com/J3J4ZUCVU)
 
 -----
 
diff --git a/pyproject.toml b/pyproject.toml
index 876c39a..c0275cf 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -45,7 +45,7 @@ Changelog = "https://github.com/blakeaw/pysb-pkpd/blob/main/CHANGELOG.md"
 # Find namespace package
 [tool.setuptools.packages.find]
 where = ["src"]
-include = ["pysb.pkpd"]
+include = ["pysb.pkpd", "pysb.pkpd.macros", "pysb.pkpd.models", "pysb.pkpd.pk_models"]
 namespaces = true
 
 # Set the dynamic version
diff --git a/src/pysb/pkpd/__init__.py b/src/pysb/pkpd/__init__.py
index 31f2014..c2e1742 100644
--- a/src/pysb/pkpd/__init__.py
+++ b/src/pysb/pkpd/__init__.py
@@ -5,4 +5,4 @@
 from .macros import *
 from .util import simulate
 
-__version__ = '0.3.0'
\ No newline at end of file
+__version__ = '0.3.1'
\ No newline at end of file
diff --git a/src/pysb/pkpd/macros.py b/src/pysb/pkpd/macros.py
index 7161b9a..6896336 100644
--- a/src/pysb/pkpd/macros.py
+++ b/src/pysb/pkpd/macros.py
@@ -4,6 +4,8 @@
 import sympy
 from sympy import Piecewise
 
+
+
 __all__ = [
     "drug_monomer",
     "one_compartment",