diff --git a/deny.toml b/deny.toml
index 19f3e1c..61d40b0 100755
--- a/deny.toml
+++ b/deny.toml
@@ -7,7 +7,8 @@ allow = [
     "Apache-2.0",
     "Apache-2.0 WITH LLVM-exception",
     "GPL-3.0",
-    "Unicode-3.0" # used for unicode-ident
+    "Unicode-3.0", # used for unicode-ident
+    "Zlib"
 ]
 confidence-threshold = 0.8