diff --git a/vyper/codegen/core.py b/vyper/codegen/core.py
index 647aa41e66..57f1432de6 100644
--- a/vyper/codegen/core.py
+++ b/vyper/codegen/core.py
@@ -673,6 +673,7 @@ def dummy_node_for_type(typ):
 
 
 def _check_assign_bytes(left, right):
+    # skip check for JSON ABI imports with length set to 0
     if left.typ.maxlen == 0:
         return