diff --git a/tests/misc.py b/tests/misc.py
index 51628f4f..580e5691 100644
--- a/tests/misc.py
+++ b/tests/misc.py
@@ -120,3 +120,12 @@ class TestMisc(unittest.TestCase):
             raise AssertionError("The following files should require gtk "
                 "version of gtk-3.8, which is what we target:\n" +
                 "\n".join([("%s version=%s" % tup) for tup in failures]))
+
+    def test_libosinfo_aliases_ro(self):
+        from virtinst import osdict
+        aliases = getattr(osdict, "_aliases")
+
+        if len(aliases) != 39:
+            raise AssertionError(_("osdict._aliases changed size. It "
+                "should never be extended, since it is only for back "
+                "compat with pre-libosinfo osdict."))
diff --git a/virtinst/osdict.py b/virtinst/osdict.py
index 76794c3b..d2eb626e 100644
--- a/virtinst/osdict.py
+++ b/virtinst/osdict.py
@@ -25,6 +25,8 @@ from datetime import datetime
 from gi.repository import Libosinfo as libosinfo
 from inspect import isfunction
 
+# This is only for back compatibility with pre-libosinfo support.
+# This should never change.
 _aliases = {
     "altlinux" : "altlinux1.0",
     "debianetch" : "debian4",