diff --git a/src/calmjs/parse/parsers/es5.py b/src/calmjs/parse/parsers/es5.py
index f2db89c..042510c 100644
--- a/src/calmjs/parse/parsers/es5.py
+++ b/src/calmjs/parse/parsers/es5.py
@@ -42,8 +42,10 @@
 
 asttypes = AstTypesFactory(pretty_print, ReprWalker())
 
-# The default values for the `Parser` constructor, passed on to ply; they must
-# be strings
+# These default values for the `Parser` constructor, passed on to ply;
+# they must be strings; these values are for reference only as
+# modifications to this value will not change what's been set up as
+# the Parser's default.
 lextab, yacctab = generate_tab_names(__name__)
 
 
diff --git a/src/calmjs/parse/parsers/optimize.py b/src/calmjs/parse/parsers/optimize.py
index ec2f569..acc6e74 100644
--- a/src/calmjs/parse/parsers/optimize.py
+++ b/src/calmjs/parse/parsers/optimize.py
@@ -115,12 +115,15 @@ def optimize_build(module_name, assume_ply_version=True):
     if assume_ply_version:
         kws['_version'] = _assume_ply_version()
 
-    paths, missing = validate_imports(*generate_tab_names(module_name, **kws))
+    lextab, yacctab = generate_tab_names(module_name, **kws)
+    paths, missing = validate_imports(lextab, yacctab)
     if missing:
         # only import, purge and regenerate if any are missing.
         unlink_modules(verify_paths(paths))
         module = import_module(module_name)
-        module.Parser()
+        # use whatever assumed version or otherwise as set up by
+        # the local generation function.
+        module.Parser(lextab=lextab, yacctab=yacctab)
 
 
 def reoptimize_all(monkey_patch=False, first_build=False):
diff --git a/src/calmjs/parse/tests/test_parsers_optimize.py b/src/calmjs/parse/tests/test_parsers_optimize.py
index 4cad624..9532035 100644
--- a/src/calmjs/parse/tests/test_parsers_optimize.py
+++ b/src/calmjs/parse/tests/test_parsers_optimize.py
@@ -121,7 +121,7 @@ def test_reoptimize_monkey_patched(self):
     def test_optimize_build(self):
         called = []
 
-        def sentinel():
+        def sentinel(*a, **kw):
             called.append(True)
 
         fake_es5 = ModuleType('fake_namespace.fake_es5')
@@ -227,7 +227,7 @@ def test_optimize_build_assume_broken_ply(self):
         optimize.ply_dist = None
         called = []
 
-        def sentinel():
+        def sentinel(*a, **kw):
             called.append(True)
 
         fake_es5 = ModuleType('fake_namespace.fake_es5')