diff --git a/netlib/websockets.py b/netlib/websockets.py
index 1e9c96cca..d5c5c2fe4 100644
--- a/netlib/websockets.py
+++ b/netlib/websockets.py
@@ -129,14 +129,12 @@ class Frame(object):
             1 <= self.opcode <= 4,
             0 <= self.mask_bit <= 1,
             1 <= self.payload_length_code <= 127,
-            self.actual_payload_length == len(self.payload)
+            self.actual_payload_length == len(self.payload),
+            1 <= len(self.masking_key) <= 4 if self.mask_bit else True,
+            self.masking_key is not None if self.mask_bit else True
         ]
         if not all(constraints):
             return False
-        elif self.mask_bit == 1 and not 1 <= len(self.masking_key) <= 4:
-            return False
-        elif self.mask_bit == 0 and self.masking_key is not None:
-            return False
         elif self.payload and self.masking_key:
             decoded = apply_mask(self.payload, self.masking_key)
             if decoded != self.decoded_payload: