diff --git a/beangulp/similar.py b/beangulp/similar.py
index 849874d0..991f950c 100644
--- a/beangulp/similar.py
+++ b/beangulp/similar.py
@@ -11,6 +11,7 @@
 from beancount.core.number import D
 from beancount.core.number import ZERO
 from beancount.core.number import ONE
+from beancount.core.number import MISSING
 from beancount.core import data
 from beancount.core import amount
 from beancount.core import interpolate
@@ -145,7 +146,7 @@ def amounts_map(entry):
         if posting.meta and interpolate.AUTOMATIC_META in posting.meta:
             continue
         currency = isinstance(posting.units, amount.Amount) and posting.units.currency
-        if isinstance(currency, str):
+        if isinstance(currency, str) and posting.units.number != MISSING:
             key = (posting.account, currency)
             amounts[key] += posting.units.number
     return amounts
diff --git a/beangulp/similar_test.py b/beangulp/similar_test.py
index 20871482..9294032d 100644
--- a/beangulp/similar_test.py
+++ b/beangulp/similar_test.py
@@ -113,6 +113,7 @@ def test_amounts_map(self, entries, _, __):
             2016-01-03 *
               Expenses:Tips         1.01 USD
               Expenses:Tips         1.02 USD
+              Expenses:Tips         USD @ 1.1 CHF
               Assets:Other
         """
         txns = list(data.filter_txns(entries))