diff --git a/jsonschema-test-suite/proc_macro/Cargo.toml b/jsonschema-test-suite/proc_macro/Cargo.toml
index 9d2fc8c..03b9479 100644
--- a/jsonschema-test-suite/proc_macro/Cargo.toml
+++ b/jsonschema-test-suite/proc_macro/Cargo.toml
@@ -28,4 +28,4 @@ regex = "1"
 quote = "1"
 serde = { version = "1", features = [ "derive" ] }
 serde_json = "1"
-syn = "1"
+syn = { version = "1", features = ["full"] }