diff --git a/scripts/choose_projects.py b/scripts/choose_projects.py
index 13ab529..eb628cf 100755
--- a/scripts/choose_projects.py
+++ b/scripts/choose_projects.py
@@ -25,7 +25,7 @@ import logging
 import os
 import platform
 import sys
-from typing import Dict, List, Set, Tuple
+from typing import Dict, List, Set, Tuple, Optional
 
 from unidiff import PatchSet
 import yaml
@@ -43,8 +43,8 @@ class ChooseProjects:
     # projects used if anything goes wrong
     FALLBACK_PROJECTS = ['all']
 
-    def __init__(self, llvm_dir: str):
-        self.llvm_dir = llvm_dir
+    def __init__(self, llvm_dir: Optional[str]):
+        self.llvm_dir = llvm_dir  # type: Optional[str]
         self.defaultProjects = dict()  # type: Dict[str, Dict[str, str]]
         self.dependencies = dict()  # type: Dict[str,List[str]]
         self.usages = dict()   # type: Dict[str,List[str]]
@@ -72,6 +72,9 @@ class ChooseProjects:
         return 'linux'
 
     def choose_projects(self, patch: str = None) -> List[str]:
+        if self.llvm_dir is None:
+            raise ValueError('path to llvm folder must be set in ChooseProject.')
+
         llvm_dir = os.path.abspath(os.path.expanduser(self.llvm_dir))
         logging.info('Scanning LLVM in {}'.format(llvm_dir))
         if not self.match_projects_dirs():
@@ -165,6 +168,11 @@ class ChooseProjects:
             result.update(changes)
         return result
 
+    def get_all_enabled_projects(self) -> List[str]:
+        """Get list of all not-excluded projects for current platform."""
+        result = set(self.all_projects) - self.excluded_projects
+        return sorted(list(result))
+
 
 if __name__ == "__main__":
     logging.basicConfig(filename='choose_projects.log', level=logging.INFO)
diff --git a/scripts/run_cmake.py b/scripts/run_cmake.py
index e22256f..fe3ef17 100755
--- a/scripts/run_cmake.py
+++ b/scripts/run_cmake.py
@@ -17,7 +17,6 @@ import argparse
 from enum import Enum
 from git import Repo
 import os
-from pathlib import Path
 import platform
 import shutil
 import subprocess
@@ -34,6 +33,11 @@ class OperatingSystem(Enum):
 
 
 class Configuration:
+    """Configuration for running cmake.
+
+    The data is mostly read from the file `run_cmake_config.yaml`
+    residing in the same folder as this script.
+    """
 
     def __init__(self, config_file_path: str):
         with open(config_file_path) as config_file:
@@ -41,7 +45,6 @@ class Configuration:
         self._environment = config['environment']  # type: Dict[OperatingSystem, Dict[str, str]]
         self.general_cmake_arguments = config['arguments']['general']  # type: List[str]
         self._specific_cmake_arguments = config['arguments']  # type: Dict[OperatingSystem, List[str]]
-        self._default_projects = config['default_projects']  # type: Dict[OperatingSystem, str]
         self.operating_system = self._detect_os()  # type: OperatingSystem
 
     @property
@@ -54,7 +57,13 @@ class Configuration:
 
     @property
     def default_projects(self) -> str:
-        return self._default_projects[self.operating_system.value]
+        """Get string of projects enabled by default.
+
+        This returns all projects in the mono repo minus the project that were
+        excluded for the current platform.
+        """
+        cp = ChooseProjects(None)
+        return ';'.join(cp.get_all_enabled_projects())
 
     @staticmethod
     def _detect_os() -> OperatingSystem:
diff --git a/scripts/run_cmake_config.yaml b/scripts/run_cmake_config.yaml
index 627c80a..7b7efb8 100644
--- a/scripts/run_cmake_config.yaml
+++ b/scripts/run_cmake_config.yaml
@@ -28,9 +28,3 @@ arguments:
     - '-DCMAKE_CXX_FLAGS=-gmlt'
   windows:
     - '-D LLVM_ENABLE_DIA_SDK=OFF'
-
-# if the automatic project detection fails or is not used, these projects are
-# enabled
-default_projects:
-  windows: 'clang;clang-tools-extra;libcxx;libc;lld;mlir;libcxxabi'
-  linux:   'clang;clang-tools-extra;libc;libcxx;libcxxabi;lld;libunwind;mlir;flang'