diff --git a/crates/ctap2-proto/Cargo.toml b/crates/ctap2-proto/Cargo.toml
index d4a9976..73a34ee 100644
--- a/crates/ctap2-proto/Cargo.toml
+++ b/crates/ctap2-proto/Cargo.toml
@@ -14,5 +14,8 @@ typed-builder = { version = "0.14.0", default-features = false }
 # Version <= to support older serde
 serde_with = { version = "<=2.2.0", optional = true }
 
+[dev-dependencies]
+hex = "0.4.3"
+
 [features]
 serde = ["dep:serde", "dep:serde_with", "fido-common/serde", "bounded-integer/serde1"]