diff --git a/circuitmatter/session.py b/circuitmatter/session.py
index 0e05adb..cb5cad4 100644
--- a/circuitmatter/session.py
+++ b/circuitmatter/session.py
@@ -324,7 +324,7 @@ def process_counter(self, counter) -> bool:
         else:
             new_bitmap = (self.window_bitmap << shift) & self.mask
             self.window_bitmap = new_bitmap
-        if 1 < shift < MSG_COUNTER_WINDOW_SIZE:
+        if 1 <= shift < MSG_COUNTER_WINDOW_SIZE:
             self.window_bitmap |= 1 << (shift - 1)
         self.message_counter = counter
         return False
diff --git a/requirements.txt b/requirements.txt
index 1e733d3..acc65ac 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,3 +1,3 @@
-cryptography==41.0.7
-ecdsa==0.18.0
-qrcode==7.4.2
+cryptography
+ecdsa
+qrcode
diff --git a/tests/test_message_reception_state.py b/tests/test_message_reception_state.py
index 71b191e..57cd853 100644
--- a/tests/test_message_reception_state.py
+++ b/tests/test_message_reception_state.py
@@ -12,13 +12,19 @@ def test_basics():
     # The current max is not ok
     assert state.process_counter(123)
 
+    # A current max + 1 is ok
+    assert not state.process_counter(124)
+
+    # Old current max isn't
+    assert state.process_counter(123)
+
     # A new value is ok
     assert not state.process_counter(126)
 
     #
     assert state.process_counter(123)
 
-    assert not state.process_counter(124)
+    assert state.process_counter(124)
 
     assert not state.process_counter(125)