diff --git a/src/iceaddr/postcodes.py b/src/iceaddr/postcodes.py
index 75e0228..23a5cea 100644
--- a/src/iceaddr/postcodes.py
+++ b/src/iceaddr/postcodes.py
@@ -1425,7 +1425,8 @@ def _filter_postcodes(key: str, searchstr: str, partial: bool = False) -> List[i
     k1 = key + "_nf"
     k2 = key + "_tgf"
 
-    for k, v in POSTCODES.items():
+    pcs = POSTCODES.items()
+    for k, v in pcs:
         nf = v[k1].lower()
         tgf = v[k2].lower()
         if (partial and (nf.startswith(p) or tgf.startswith(p))) or p in (nf, tgf):
diff --git a/tests/test_iceaddr.py b/tests/test_iceaddr.py
index 244d96a..2d7e0e8 100644
--- a/tests/test_iceaddr.py
+++ b/tests/test_iceaddr.py
@@ -31,12 +31,12 @@
 
 def test_address_lookup():
     """Test address lookup using various known addresses."""
-    ADDR_TO_POSTCODE = [
+    ADDR_TO_POSTCODE = (
         ("Öldugata", 4, "Reykjavík", 101),
         ("öldugötu", 12, "hafnarfirði", 220),
         ("Tómasarhaga", 12, "Reykjavík", 107),
         ("smiðjuvegur", 22, "", 200),
-    ]
+    )
 
     for a in ADDR_TO_POSTCODE:
         res = iceaddr_lookup(a[0], number=a[1], placename=a[2])
@@ -45,7 +45,7 @@ def test_address_lookup():
     res = iceaddr_lookup("Brattagata", number=4, letter="b")
     assert res and res[0]["postnr"] == 310 and res[0]["stadur_nf"] == "Borgarnes"
 
-    POSTCODE_TO_PLACENAME = [
+    POSTCODE_TO_PLACENAME = (
         ("Öldugata", 4, 101, "Reykjavík", "Höfuðborgarsvæðið", "Þéttbýli"),
         (
             "dagverðardalur",
@@ -56,7 +56,7 @@ def test_address_lookup():
             "Þéttbýli",
         ),
         ("Höfðabraut", 3, 805, "Selfoss", "Suðurland og Reykjanes", "Stærra dreifbýli"),
-    ]
+    )
 
     for p in POSTCODE_TO_PLACENAME:
         # print(f"iceaddr_lookup('{p[0]}', number={p[1]}, postcode={p[2]}"