diff --git a/conservancy_beancount/plugin/__init__.py b/conservancy_beancount/plugin/__init__.py
index 3c88423..cbcb880 100644
--- a/conservancy_beancount/plugin/__init__.py
+++ b/conservancy_beancount/plugin/__init__.py
@@ -86,8 +86,8 @@ def run(entries, options_map, config='', hook_registry=HOOK_REGISTRY):
         for hook in hooks[entry_type]:
             errors.extend(hook.run(entry))
         if entry_type == 'Transaction':
-            for post in entry.postings:
+            for index, post in enumerate(entry.postings):
                 for hook in hooks['Posting']:
-                    errors.extend(hook.run(entry, post))
+                    errors.extend(hook.run(entry, post, index))
     return entries, errors
 
diff --git a/conservancy_beancount/plugin/core.py b/conservancy_beancount/plugin/core.py
index fc8a130..ddf2437 100644
--- a/conservancy_beancount/plugin/core.py
+++ b/conservancy_beancount/plugin/core.py
@@ -132,10 +132,11 @@ class PostingChecker:
         except (KeyError, TypeError):
             return txn.meta.get(key, default)
 
-    def _meta_set(self, post, key, value):
+    def _meta_set(self, txn, post, post_index, key, value):
         if post.meta is None:
-            post.meta = {}
-        post.meta[key] = value
+            txn.postings[post_index] = Posting(*post[:5], {key: value})
+        else:
+            post.meta[key] = value
 
     # If the posting does not specify METADATA_KEY, the hook calls
     # _default_value to get a default. This method should either return
diff --git a/tests/test_meta_expenseAllocation.py b/tests/test_meta_expenseAllocation.py
index 33240dc..2c01e41 100644
--- a/tests/test_meta_expenseAllocation.py
+++ b/tests/test_meta_expenseAllocation.py
@@ -42,7 +42,7 @@ def test_valid_values_on_postings(src_value, set_value):
         ('Expenses:General', 25, {'expenseAllocation': src_value}),
     ])
     checker = meta_expense_allocation.MetaExpenseAllocation()
-    errors = checker.run(txn, txn.postings[-1])
+    errors = checker.run(txn, txn.postings[-1], -1)
     assert not errors
     assert txn.postings[-1].meta.get('expenseAllocation') == set_value
 
@@ -53,7 +53,7 @@ def test_invalid_values_on_postings(src_value):
         ('Expenses:General', 25, {'expenseAllocation': src_value}),
     ])
     checker = meta_expense_allocation.MetaExpenseAllocation()
-    errors = checker.run(txn, txn.postings[-1])
+    errors = checker.run(txn, txn.postings[-1], -1)
     assert errors
 
 @pytest.mark.parametrize('src_value,set_value', VALID_VALUES.items())
@@ -63,7 +63,7 @@ def test_valid_values_on_transactions(src_value, set_value):
         ('Expenses:General', 25),
     ])
     checker = meta_expense_allocation.MetaExpenseAllocation()
-    errors = checker.run(txn, txn.postings[-1])
+    errors = checker.run(txn, txn.postings[-1], -1)
     assert not errors
     assert txn.postings[-1].meta.get('expenseAllocation') == set_value
 
@@ -74,7 +74,7 @@ def test_invalid_values_on_transactions(src_value):
         ('Expenses:General', 25),
     ])
     checker = meta_expense_allocation.MetaExpenseAllocation()
-    errors = checker.run(txn, txn.postings[-1])
+    errors = checker.run(txn, txn.postings[-1], -1)
     assert errors
 
 @pytest.mark.parametrize('account', [
@@ -90,7 +90,7 @@ def test_non_expense_accounts_skipped(account):
         ('Expenses:General', 25, {'expenseAllocation': 'program'}),
     ])
     checker = meta_expense_allocation.MetaExpenseAllocation()
-    errors = checker.run(txn, txn.postings[0])
+    errors = checker.run(txn, txn.postings[0], 0)
     assert not errors
 
 @pytest.mark.parametrize('account,set_value', [
@@ -106,7 +106,7 @@ def test_default_values(account, set_value):
         (account, 25),
     ])
     checker = meta_expense_allocation.MetaExpenseAllocation()
-    errors = checker.run(txn, txn.postings[-1])
+    errors = checker.run(txn, txn.postings[-1], -1)
     assert not errors
     assert txn.postings[-1].meta['expenseAllocation'] == set_value
 
@@ -123,7 +123,7 @@ def test_default_value_set_in_date_range(date, set_value):
         ('Expenses:General', 25),
     ])
     checker = meta_expense_allocation.MetaExpenseAllocation()
-    errors = checker.run(txn, txn.postings[-1])
+    errors = checker.run(txn, txn.postings[-1], -1)
     assert not errors
     got_value = (txn.postings[-1].meta or {}).get('expenseAllocation')
     assert bool(got_value) == bool(set_value)
diff --git a/tests/test_meta_taxImplication.py b/tests/test_meta_taxImplication.py
index fe2a794..d745a16 100644
--- a/tests/test_meta_taxImplication.py
+++ b/tests/test_meta_taxImplication.py
@@ -54,7 +54,7 @@ def test_valid_values_on_postings(src_value, set_value):
         ('Assets:Cash', -25, {'taxImplication': src_value}),
     ])
     checker = meta_tax_implication.MetaTaxImplication()
-    errors = checker.run(txn, txn.postings[-1])
+    errors = checker.run(txn, txn.postings[-1], -1)
     assert not errors
     assert txn.postings[-1].meta.get('taxImplication') == set_value
 
@@ -65,7 +65,7 @@ def test_invalid_values_on_postings(src_value):
         ('Assets:Cash', -25, {'taxImplication': src_value}),
     ])
     checker = meta_tax_implication.MetaTaxImplication()
-    errors = checker.run(txn, txn.postings[-1])
+    errors = checker.run(txn, txn.postings[-1], -1)
     assert errors
 
 @pytest.mark.parametrize('src_value,set_value', VALID_VALUES.items())
@@ -75,7 +75,7 @@ def test_valid_values_on_transactions(src_value, set_value):
         ('Assets:Cash', -25),
     ])
     checker = meta_tax_implication.MetaTaxImplication()
-    errors = checker.run(txn, txn.postings[-1])
+    errors = checker.run(txn, txn.postings[-1], -1)
     assert not errors
     assert txn.postings[-1].meta.get('taxImplication') == set_value
 
@@ -86,7 +86,7 @@ def test_invalid_values_on_transactions(src_value):
         ('Assets:Cash', -25),
     ])
     checker = meta_tax_implication.MetaTaxImplication()
-    errors = checker.run(txn, txn.postings[-1])
+    errors = checker.run(txn, txn.postings[-1], -1)
     assert errors
 
 @pytest.mark.parametrize('account', [
@@ -100,7 +100,7 @@ def test_non_asset_accounts_skipped(account):
         ('Assets:Cash', -25, {'taxImplication': 'USA-Corporation'}),
     ])
     checker = meta_tax_implication.MetaTaxImplication()
-    errors = checker.run(txn, txn.postings[0])
+    errors = checker.run(txn, txn.postings[0], 0)
     assert not errors
 
 def test_asset_credits_skipped():
@@ -109,7 +109,7 @@ def test_asset_credits_skipped():
         ('Assets:Cash', 25),
     ])
     checker = meta_tax_implication.MetaTaxImplication()
-    errors = checker.run(txn, txn.postings[-1])
+    errors = checker.run(txn, txn.postings[-1], -1)
     assert not errors
     assert not txn.postings[-1].meta
 
@@ -126,5 +126,5 @@ def test_default_value_set_in_date_range(date, need_value):
         ('Assets:Cash', -25),
     ])
     checker = meta_tax_implication.MetaTaxImplication()
-    errors = checker.run(txn, txn.postings[-1])
+    errors = checker.run(txn, txn.postings[-1], -1)
     assert bool(errors) == bool(need_value)
diff --git a/tests/test_plugin_run.py b/tests/test_plugin_run.py
index 5211934..4283829 100644
--- a/tests/test_plugin_run.py
+++ b/tests/test_plugin_run.py
@@ -35,7 +35,7 @@ class TransactionCounter:
 class PostingCounter(TransactionCounter):
     HOOK_GROUPS = frozenset(['Posting', 'counter'])
 
-    def run(self, txn, post):
+    def run(self, txn, post, post_index):
         return ['post:{}'.format(id(post))]
 
 
diff --git a/tests/testutil.py b/tests/testutil.py
index c113e1b..7fc3815 100644
--- a/tests/testutil.py
+++ b/tests/testutil.py
@@ -33,6 +33,8 @@ def parse_date(s, fmt='%Y-%m-%d'):
 def Posting(account, number,
             currency='USD', cost=None, price=None, flag=None,
             **meta):
+    if not meta:
+        meta = None
     return bc_data.Posting(
         account,
         bc_amount.Amount(Decimal(number), currency),