diff --git a/mesonbuild/coredata.py b/mesonbuild/coredata.py
index 0c2f501..b12ec82 100644
--- a/mesonbuild/coredata.py
+++ b/mesonbuild/coredata.py
@@ -575,6 +575,11 @@
         self.cross_files = self.__load_config_files(options, scratch_dir, 'cross')
         self.compilers: PerMachine[T.Dict[str, Compiler]] = PerMachine(OrderedDict(), OrderedDict())
 
+        # Stores the (name, hash) of the options file, The name will be either
+        # "meson_options.txt" or "meson.options".
+        # This is used by mconf to reload the option file if it's changed.
+        self.options_files: T.Dict[SubProject, T.Optional[T.Tuple[str, str]]] = {}
+
         # Set of subprojects that have already been initialized once, this is
         # required to be stored and reloaded with the coredata, as we don't
         # want to overwrite options for such subprojects.
diff --git a/mesonbuild/interpreter/interpreter.py b/mesonbuild/interpreter/interpreter.py
index d870de1..2c1ac89 100644
--- a/mesonbuild/interpreter/interpreter.py
+++ b/mesonbuild/interpreter/interpreter.py
@@ -4,6 +4,8 @@
 
 from __future__ import annotations
 
+import hashlib
+
 from .. import mparser
 from .. import environment
 from .. import coredata
@@ -1187,10 +1189,16 @@
         else:
             option_file = old_option_file
         if os.path.exists(option_file):
+            with open(option_file, 'rb') as f:
+                # We want fast, not cryptographically secure, this is just to see of
+                # the option file has changed
+                self.coredata.options_files[self.subproject] = (option_file, hashlib.sha1(f.read()).hexdigest())
             oi = optinterpreter.OptionInterpreter(self.subproject)
             oi.process(option_file)
             self.coredata.update_project_options(oi.options, self.subproject)
             self.add_build_def_file(option_file)
+        else:
+            self.coredata.options_files[self.subproject] = None
 
         if self.subproject:
             self.project_default_options = {k.evolve(subproject=self.subproject): v