diff --git a/tests/json_parser.rs b/tests/json_parser.rs
index fc20614..da3f391 100644
--- a/tests/json_parser.rs
+++ b/tests/json_parser.rs
@@ -61,8 +61,13 @@ fn json_bool<'a>() -> impl JsonParser<'a, JsonValue> {
 }
 
 fn json_number<'a>() -> impl JsonParser<'a, JsonValue> {
-    let digit = || one_of("1234567890");
-    let digits = || repeated(digit()).at_least(1);
+    fn digit<'a>() -> impl JsonParser<'a, &'a str> {
+        one_of("1234567890")
+    }
+
+    fn digits<'a>() -> impl JsonParser<'a, Vec<&'a str>> {
+        repeated(digit()).at_least(1)
+    }
 
     let json_number_inner = choice((
         seq((digits(), literal(".").ignore_then(digits()).optional())).map(