diff --git a/core/src/apps/management/recovery_device/word_validity.py b/core/src/apps/management/recovery_device/word_validity.py
index 915cb0323..10950e0a6 100644
--- a/core/src/apps/management/recovery_device/word_validity.py
+++ b/core/src/apps/management/recovery_device/word_validity.py
@@ -16,10 +16,7 @@ NOK_THRESHOLD_REACHED = const(3)
 
 
 def check(
-    current_index: int,
-    current_word: str,
-    backup_type: Optional[EnumTypeBackupType],
-    previous_words: List[str],
+    backup_type: Optional[EnumTypeBackupType], partial_mnemonic: List[str]
 ) -> int:
     # we can't perform any checks if the backup type was not yet decided
     if backup_type is None:
@@ -34,22 +31,22 @@ def check(
         raise RuntimeError
 
     if backup_type == BackupType.Slip39_Basic:
-        return check_slip39_basic(current_index, current_word, previous_mnemonics)
+        return check_slip39_basic(partial_mnemonic, previous_mnemonics)
 
     if backup_type == BackupType.Slip39_Advanced:
-        return check_slip39_advanced(
-            current_index, current_word, previous_words, previous_mnemonics
-        )
+        return check_slip39_advanced(partial_mnemonic, previous_mnemonics)
 
     # there are no other backup types
     raise RuntimeError
 
 
 def check_slip39_basic(
-    current_index: int, current_word: str, previous_mnemonics: List[List[str]]
+    partial_mnemonic: List[str], previous_mnemonics: List[List[str]]
 ) -> int:
     # check if first 3 words of mnemonic match
     # we can check against the first one, others were checked already
+    current_index = len(partial_mnemonic) - 1
+    current_word = partial_mnemonic[-1]
     if current_index < 3:
         share_list = previous_mnemonics[0][0].split(" ")
         if share_list[current_index] != current_word:
@@ -65,11 +62,10 @@ def check_slip39_basic(
 
 
 def check_slip39_advanced(
-    current_index: int,
-    current_word: str,
-    previous_words: List[str],
-    previous_mnemonics: List[List[str]],
+    partial_mnemonic: List[str], previous_mnemonics: List[List[str]]
 ) -> int:
+    current_index = len(partial_mnemonic) - 1
+    current_word = partial_mnemonic[-1]
     if current_index < 2:
         share_list = next(s for s in previous_mnemonics if s)[0].split(" ")
         if share_list[current_index] != current_word:
@@ -87,7 +83,7 @@ def check_slip39_advanced(
     # check if share was already added for group
     elif current_index == 3:
         # we use the 3rd word from previously entered shares to find the group id
-        group_identifier_word = previous_words[2]
+        group_identifier_word = partial_mnemonic[2]
         group_index = None
         for i, group in enumerate(previous_mnemonics):
             if len(group) > 0:
diff --git a/core/tests/test_apps.management.recovery_device.py b/core/tests/test_apps.management.recovery_device.py
index eab24e7e1..497fa4d6a 100644
--- a/core/tests/test_apps.management.recovery_device.py
+++ b/core/tests/test_apps.management.recovery_device.py
@@ -4,6 +4,8 @@ from mock_storage import mock_storage
 import storage
 import storage.recovery
 from apps.management.recovery_device.recover import process_slip39
+from trezor.messages import BackupType
+from apps.management.recovery_device.word_validity import check, OK, NOK_IDENTIFIER_MISMATCH, NOK_ALREADY_ADDED, NOK_THRESHOLD_REACHED
 
 MNEMONIC_SLIP39_BASIC_20_3of6 = [
     "extra extend academic bishop cricket bundle tofu goat apart victim enlarge program behavior permit course armed jerky faint language modern",
@@ -142,21 +144,18 @@ class TestSlip39(unittest.TestCase):
 
     @mock_storage
     def test_check_word_validity(self):
-        from trezor.messages import BackupType
-        from apps.management.recovery_device.word_validity import check, OK, NOK_IDENTIFIER_MISMATCH, NOK_ALREADY_ADDED, NOK_THRESHOLD_REACHED
-
         storage.recovery.set_in_progress(True)
 
-        # nothing is stored -> should raise
+        # We claim to know the backup type, but nothing is stored. That is an invalid state.
         with self.assertRaises(RuntimeError):
-            check(0, "ocean", BackupType.Slip39_Advanced, [])
+            check(BackupType.Slip39_Advanced, ["ocean"])
 
         # if backup type is not set we can not do any checks
-        result = check(0, "ocean", None, [])
+        result = check(None, ["ocean"])
         self.assertIs(result, OK)
 
         # BIP-39 has no "on-the-fly" checks
-        result = check(0, "ocean", BackupType.Bip39, [])
+        result = check(BackupType.Bip39, ["ocean"])
         self.assertIs(result, OK)
 
         # let's store two shares in the storage
@@ -166,15 +165,15 @@ class TestSlip39(unittest.TestCase):
         self.assertIsNone(secret)
 
         # different identifier
-        result = check(0, "slush", BackupType.Slip39_Advanced, [])
+        result = check(BackupType.Slip39_Advanced, ["slush"])
         self.assertIs(result, NOK_IDENTIFIER_MISMATCH)
 
         # same first word but still a different identifier
-        result = check(1, "slush", BackupType.Slip39_Advanced, ["trash"])
+        result = check(BackupType.Slip39_Advanced, ["trash", "slush"])
         self.assertIs(result, NOK_IDENTIFIER_MISMATCH)
 
         # same mnemonic found out using the index
-        result = check(3, "ambition", BackupType.Slip39_Advanced, ["trash", "smug", "adjust"])
+        result = check(BackupType.Slip39_Advanced, ["trash", "smug", "adjust", "ambition"])
         self.assertIs(result, NOK_ALREADY_ADDED)
 
         # Let's store two more. The group is 4/6 so this group is now complete.
@@ -184,7 +183,7 @@ class TestSlip39(unittest.TestCase):
         self.assertIsNone(secret)
 
         # If trying to add another one from this group we get a warning.
-        result = check(2, "adjust", BackupType.Slip39_Advanced, ["trash", "smug"])
+        result = check(BackupType.Slip39_Advanced, ["trash", "smug", "adjust"])
         self.assertIs(result, NOK_THRESHOLD_REACHED)