diff --git a/pylnk3.py b/pylnk3.py
index 2bd6df1..f037c90 100644
--- a/pylnk3.py
+++ b/pylnk3.py
@@ -1448,7 +1448,8 @@ def __init__(self, lnk=None, blocks=None):
             signature = read_int(lnk)
             bytes = lnk.read(size-8)
             # lnk.seek(-8, 1)
-            block_type = EXTRA_DATA_TYPES[signature]
+            # gracefully handle unknown ExtraData block signature
+            block_type = EXTRA_DATA_TYPES.get(signature)
             if block_type in EXTRA_DATA_TYPES_CLASSES:
                 block_class = EXTRA_DATA_TYPES_CLASSES[block_type]
                 block = block_class(bytes=bytes)