diff --git a/build/moz.configure/toolchain.configure b/build/moz.configure/toolchain.configure
index edcb2c0e2807..dea774dc031e 100644
--- a/build/moz.configure/toolchain.configure
+++ b/build/moz.configure/toolchain.configure
@@ -84,29 +84,6 @@ option(
     nargs=1,
 )
 
-# Version defines
-# ==============================================================
-
-
-# For extensions and langpacks, we require a max version that is compatible
-# across security releases. MOZ_APP_MAXVERSION is our method for doing that.
-# 24.0a1 and 24.0a2 aren't affected
-# 24.0 becomes 24.*
-# 24.1.1 becomes 24.*
-@depends(milestone.app_version, build_project)
-def moz_app_maxversion(app_version, build_project):
-    if "a" not in app_version:
-        version = Version(app_version)
-        if build_project == "suite":
-            return f"{version.major}.{version.minor}.*"
-        else:
-            return f"{version.major}.*"
-    else:
-        return app_version
-
-
-set_config("MOZ_APP_MAXVERSION", moz_app_maxversion)
-
 
 # Code optimization
 # ==============================================================
diff --git a/old-configure.in b/old-configure.in
index edbb689c45ab..3dd07e74cd11 100644
--- a/old-configure.in
+++ b/old-configure.in
@@ -140,10 +140,30 @@ AC_SUBST(MOZ_EME_PROCESS_BUNDLEID)
 # version_display.txt or version.txt in the application directory, or
 # browser/config/version_display.txt.
 
+# For extensions and langpacks, we require a max version that is compatible
+# across security releases. MOZ_APP_MAXVERSION is our method for doing that.
+# 24.0a1 and 24.0a2 aren't affected
+# 24.0 becomes 24.*
+# 24.1.1 becomes 24.*
+IS_ALPHA=`echo $MOZ_APP_VERSION | grep a`
+if test -z "$IS_ALPHA"; then
+  changequote(,)
+  if test "$(basename $MOZ_BUILD_APP)" = "suite"; then
+    MOZ_APP_MAXVERSION=`echo $MOZ_APP_VERSION | sed "s|\(^[0-9]*\.[0-9]*\).*|\1|"`.*
+  else
+    MOZ_APP_MAXVERSION=`echo $MOZ_APP_VERSION | sed "s|\(^[0-9]*\).*|\1|"`.*
+  fi
+  changequote([,])
+else
+  MOZ_APP_MAXVERSION=$MOZ_APP_VERSION
+fi
+
 AC_SUBST(MOZ_APP_DISPLAYNAME)
 AC_SUBST(MOZ_APP_PROFILE)
 AC_DEFINE_UNQUOTED(MOZ_APP_UA_VERSION, "$MOZ_APP_VERSION")
 
+AC_SUBST(MOZ_APP_MAXVERSION)
+
 dnl Set various defines and substitutions
 dnl ========================================================