patch.diff

diff --git a/cMake/FreeCAD_Helpers/SetupPython.cmake b/cMake/FreeCAD_Helpers/SetupPython.cmake
index a2887affcb..6043fba779 100644
--- a/cMake/FreeCAD_Helpers/SetupPython.cmake
+++ b/cMake/FreeCAD_Helpers/SetupPython.cmake
@@ -18,4 +18,12 @@ macro(SetupPython)
          message(FATAL_ERROR "To build FreeCAD you need at least Python 3.8\n")
     endif()
 
+    # If a custom Python directory was passed in, then save it as PYTHON_HOME_DIR,
+    # which is used by config.h.cmake when generating the config header file.
+    if (DEFINED Python3_ROOT_DIR)
+        set(HAVE_PYTHON_HOME_DIR ON)
+        file(REAL_PATH "${Python3_ROOT_DIR}" PYTHON_HOME_DIR)
+    endif ()
+
+
 endmacro(SetupPython)
diff --git a/src/config.h.cmake b/src/config.h.cmake
index 97c068e6cf..2208fc48a8 100644
--- a/src/config.h.cmake
+++ b/src/config.h.cmake
@@ -117,6 +117,12 @@
 /* Define to 1 if you have a C runtime with backtrace symbols. */
 #cmakedefine HAVE_BACKTRACE_SYMBOLS
 
+/* Define to 1 if we have a custom Python home root directory. */
+#cmakedefine HAVE_PYTHON_HOME_DIR
+
+/* Path to the custom Python home root directory (PYTHONHOME) */
+#define PYTHON_HOME_DIR "${PYTHON_HOME_DIR}"
+
 /* Name of package */
 #define PACKAGE "FreeCAD"