diff --git a/src/appenv.py b/src/appenv.py
index 15b1478..58974ef 100755
--- a/src/appenv.py
+++ b/src/appenv.py
@@ -28,6 +28,14 @@
 import re
 
 
+class TColors:
+    """Terminal colors for pretty output."""
+    RED = '\033[91m'
+    GREEN = '\033[92m'
+    YELLOW = '\033[93m'
+    RESET = '\033[0m'
+
+
 def cmd(c, merge_stderr=True, quiet=False):
     # TODO revisit the cmd() architecture w/ python 3
     # XXX better IO management for interactive output and seeing original
@@ -134,8 +142,7 @@ def ensure_venv(target):
     pip(target, ["install", "--upgrade", "pip"])
 
 
-def ensure_minimal_python():
-    current_python = os.path.realpath(sys.executable)
+def parse_preferences():
     preferences = None
     if os.path.exists('requirements.txt'):
         with open('requirements.txt') as f:
@@ -148,9 +155,15 @@ def ensure_minimal_python():
                 preferences = [x.strip() for x in preferences.split(',')]
                 preferences = list(filter(None, preferences))
                 break
+    return preferences
+
+
+def ensure_minimal_python():
+    current_python = os.path.realpath(sys.executable)
+    preferences = parse_preferences()
     if not preferences:
         # We have no preferences defined, use the current python.
-        print("Update lockfile with with {}.".format(current_python))
+        print("Updating lockfile with with {}.".format(current_python))
         print("If you want to use a different version, set it via")
         print(" `# appenv-python-preference:` in requirements.txt.")
         return
@@ -194,20 +207,18 @@ def ensure_best_python(base):
         return
     import shutil
 
-    # use newest Python available if nothing else is requested
-    preferences = ['3.{}'.format(x) for x in reversed(range(4, 20))]
+    preferences = parse_preferences()
 
-    if os.path.exists('requirements.txt'):
-        with open('requirements.txt') as f:
-            for line in f:
-                # Expected format:
-                # # appenv-python-preference: 3.1,3.9,3.4
-                if not line.startswith("# appenv-python-preference: "):
-                    continue
-                preferences = line.split(':')[1]
-                preferences = [x.strip() for x in preferences.split(',')]
-                preferences = list(filter(None, preferences))
-                break
+    if preferences is None:
+        if sys.version_info >= (3, 12):
+            print("You are using a Python version >= 3.12.")
+            print(
+                "Please specify a Python version in the requirements.txt file."
+            )
+            print("Lockfiles created with a Python version lower than 3.12")
+            print("may create a broken venv with a Python version >= 3.12.")
+        # use newest Python available if nothing else is requested
+        preferences = ['3.{}'.format(x) for x in reversed(range(4, 20))]
 
     current_python = os.path.realpath(sys.executable)
     for version in preferences:
@@ -505,6 +516,12 @@ def reset(self, args=None, remaining=None):
 
     def update_lockfile(self, args=None, remaining=None):
         ensure_minimal_python()
+        preferences = parse_preferences()
+        python312_mixed_setuptools_workaround = False
+        if preferences is not None:
+            if any(f'3.{x}' in preferences for x in range(4, 12)):
+                if any(f'3.{x}' in preferences for x in range(12, 20)):
+                    python312_mixed_setuptools_workaround = True
         os.chdir(self.base)
         print("Updating lockfile")
         tmpdir = os.path.join(self.appenv_dir, "updatelock")
@@ -515,7 +532,12 @@ def update_lockfile(self, args=None, remaining=None):
         pip(tmpdir, ["install", "-r", "requirements.txt"])
 
         extra_specs = []
-        result = pip(tmpdir, ["freeze"], merge_stderr=False).decode('ascii')
+        pip_freeze_args = ["freeze"]
+        if python312_mixed_setuptools_workaround:
+            pip_freeze_args.extend(["--all", "--exclude", "pip"])
+        result = pip(
+            tmpdir, pip_freeze_args, merge_stderr=False).decode('ascii')
+        # They changed this behaviour in https://github.com/pypa/pip/pull/12032
         pinned_versions = {}
         for line in result.splitlines():
             if line.strip().startswith('-e '):