diff --git a/game/savecompat.py b/game/savecompat.py
new file mode 100644
index 00000000..5388dd24
--- /dev/null
+++ b/game/savecompat.py
@@ -0,0 +1,48 @@
+"""Tools for aiding in save compat removal after compatibility breaks."""
+from collections import Callable
+from typing import TypeVar
+
+from game.version import MAJOR_VERSION
+
+ReturnT = TypeVar("ReturnT")
+
+
+class DeprecatedSaveCompatError(RuntimeError):
+    def __init__(self, function_name: str) -> None:
+        super().__init__(
+            f"{function_name} has save compat code for a different major version."
+        )
+
+
+def has_save_compat_for(
+    major: int,
+) -> Callable[[Callable[..., ReturnT]], Callable[..., ReturnT]]:
+    """Declares a function or method as having save compat code for a given version.
+
+    If the function has save compatibility for the current major version, there is no
+    change in behavior.
+
+    If the function has save compatibility for a *different* (future or past) major
+    version, DeprecatedSaveCompatError will be raised during startup. Since a break in
+    save compatibility is the definition of a major version break, there's no need to
+    keep around old save compat code; it only serves to mask initialization bugs.
+
+    Args:
+        major: The major version for which the decorated function has save
+        compatibility.
+
+    Returns:
+        The decorated function or method.
+
+    Raises:
+        DeprecatedSaveCompatError: The decorated function has save compat code for
+        another version of liberation, and that code (and the decorator declaring it)
+        should be removed from this branch.
+    """
+
+    def decorator(func: Callable[..., ReturnT]) -> Callable[..., ReturnT]:
+        if major != MAJOR_VERSION:
+            raise DeprecatedSaveCompatError(func.__name__)
+        return func
+
+    return decorator
diff --git a/game/version.py b/game/version.py
index c25490e0..7c989e2a 100644
--- a/game/version.py
+++ b/game/version.py
@@ -1,8 +1,15 @@
 from pathlib import Path
 
 
+MAJOR_VERSION = 5
+MINOR_VERSION = 0
+MICRO_VERSION = 0
+
+
 def _build_version_string() -> str:
-    components = ["5.0.0"]
+    components = [
+        ".".join(str(v) for v in (MAJOR_VERSION, MINOR_VERSION, MICRO_VERSION))
+    ]
     build_number_path = Path("resources/buildnumber")
     if build_number_path.exists():
         with build_number_path.open("r") as build_number_file: