diff --git a/exercises/15_traits/traits4.rs b/exercises/15_traits/traits4.rs
index ed63f6e1..80092a64 100644
--- a/exercises/15_traits/traits4.rs
+++ b/exercises/15_traits/traits4.rs
@@ -1,23 +1,18 @@
-// Your task is to replace the '??' sections so the code compiles.
-//
-// Don't change any line other than the marked one.
-
 trait Licensed {
     fn licensing_info(&self) -> String {
-        "some information".to_string()
+        "Default license".to_string()
     }
 }
 
-struct SomeSoftware {}
-
-struct OtherSoftware {}
+struct SomeSoftware;
+struct OtherSoftware;
 
 impl Licensed for SomeSoftware {}
 impl Licensed for OtherSoftware {}
 
-// YOU MAY ONLY CHANGE THE NEXT LINE
-fn compare_license_types(software: ??, software_two: ??) -> bool {
-    software.licensing_info() == software_two.licensing_info()
+// TODO: Fix the compiler error by only changing the signature of this function.
+fn compare_license_types(software1: ???, software2: ???) -> bool {
+    software1.licensing_info() == software2.licensing_info()
 }
 
 fn main() {
@@ -30,17 +25,11 @@ mod tests {
 
     #[test]
     fn compare_license_information() {
-        let some_software = SomeSoftware {};
-        let other_software = OtherSoftware {};
-
-        assert!(compare_license_types(some_software, other_software));
+        assert!(compare_license_types(SomeSoftware, OtherSoftware));
     }
 
     #[test]
     fn compare_license_information_backwards() {
-        let some_software = SomeSoftware {};
-        let other_software = OtherSoftware {};
-
-        assert!(compare_license_types(other_software, some_software));
+        assert!(compare_license_types(OtherSoftware, SomeSoftware));
     }
 }
diff --git a/rustlings-macros/info.toml b/rustlings-macros/info.toml
index 92e440ae..43ccdf80 100644
--- a/rustlings-macros/info.toml
+++ b/rustlings-macros/info.toml
@@ -784,9 +784,10 @@ name = "traits4"
 dir = "15_traits"
 hint = """
 Instead of using concrete types as parameters you can use traits. Try replacing
-the '??' with 'impl [what goes here?]'
+`???` with `impl [what goes here?]`.
 
-See the documentation at: https://doc.rust-lang.org/book/ch10-02-traits.html#traits-as-parameters"""
+Related section in The Book:
+https://doc.rust-lang.org/book/ch10-02-traits.html#traits-as-parameters"""
 
 [[exercises]]
 name = "traits5"
diff --git a/solutions/15_traits/traits4.rs b/solutions/15_traits/traits4.rs
index 4e181989..78b5a110 100644
--- a/solutions/15_traits/traits4.rs
+++ b/solutions/15_traits/traits4.rs
@@ -1 +1,34 @@
-// Solutions will be available before the stable release. Thank you for testing the beta version 🥰
+trait Licensed {
+    fn licensing_info(&self) -> String {
+        "Default license".to_string()
+    }
+}
+
+struct SomeSoftware;
+struct OtherSoftware;
+
+impl Licensed for SomeSoftware {}
+impl Licensed for OtherSoftware {}
+
+fn compare_license_types(software1: impl Licensed, software2: impl Licensed) -> bool {
+    software1.licensing_info() == software2.licensing_info()
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn compare_license_information() {
+        assert!(compare_license_types(SomeSoftware, OtherSoftware));
+    }
+
+    #[test]
+    fn compare_license_information_backwards() {
+        assert!(compare_license_types(OtherSoftware, SomeSoftware));
+    }
+}