diff --git a/package_builder/common_build_python.bat b/package_builder/common_build_python.bat
index ba4529e..cb75e8b 100644
--- a/package_builder/common_build_python.bat
+++ b/package_builder/common_build_python.bat
@@ -14,8 +14,6 @@ set PYTHON3W=%PYTHONDIR%\pythonw.exe
 set PYTHOND=%PYTHONDIR%\python_d.exe
 set PYTHON3D=%PYTHONDIR%\python_d.exe
 
-set PIP_CONSTRAINT=%~dp0\constraints.txt
-
 git clean -fqdX %PYTHONDIR%\Lib\
 del /q /f %PYTHONDIR%\*.exe
 del /q /f %PYTHONDIR%\*.dll
@@ -64,7 +62,7 @@ if %errorlevel% geq 4 (
 
 set ZIPEXE=C:\"Program Files"\7-Zip\7z.exe
 
-set PYTHONVER=3.12
+set PYTHONVER=3.13
 set PYTHONPATCH=9
 set PYTHONVERND=%PYTHONVER:.=%
 
@@ -86,7 +84,7 @@ set "PATH=%PYTHONDIR%\Scripts;%PATH%"
 %PYTHON% -m pip install --cache-dir %~dp0\.pip_cache --upgrade pip --log %~dp0\pip_upgrade.log
 if %errorlevel% neq 0 exit /b %errorlevel%
 
-%PYTHON% -m pip install --cache-dir %~dp0\.pip_cache -r %~dp0\requirements.txt --no-warn-script-location --log %~dp0\pip_requirements.log
+%PYTHON% -m pip install -v --cache-dir %~dp0\.pip_cache -r %~dp0\requirements.txt --no-warn-script-location --log %~dp0\pip_requirements.log --constraint %~dp0\constraints.txt --build-constraint %~dp0\constraints.txt
 if %errorlevel% neq 0 exit /b %errorlevel%
 
 cd %~dp0
diff --git a/package_builder/constraints.txt b/package_builder/constraints.txt
index f0f84f2..79221fa 100644
--- a/package_builder/constraints.txt
+++ b/package_builder/constraints.txt
@@ -1,4 +1,4 @@
-epicscorelibs @ https://github.com/ISISComputingGroup/epicscorelibs/releases/download/epicscorelibs-7.0.7.99.1.2-isis/epicscorelibs-7.0.7.99.1.2-cp312-cp312-win_amd64.whl
-pcaspy @ git+https://github.com/ISISComputingGroup/pcaspy
+epicscorelibs @ https://github.com/ISISComputingGroup/epicscorelibs/releases/download/epicscorelibs-7.0.7.99.1.2-isis/epicscorelibs-7.0.7.99.1.2-cp313-cp313-win_amd64.whl
+pcaspy @ git+https://github.com/ISISComputingGroup/pcaspy.git
 CaChannel @ git+https://github.com/ISISComputingGroup/CaChannel.git
 numpy>=2
diff --git a/package_builder/requirements.txt b/package_builder/requirements.txt
index 9dc7ab8..c435f20 100644
--- a/package_builder/requirements.txt
+++ b/package_builder/requirements.txt
@@ -14,7 +14,6 @@ cycler
 cython
 decorator
 docutils
-epicscorelibs
 ess-streaming-data-types
 funcsigs
 future