diff --git a/src/sink.rs b/src/sink.rs
index 92e56af..a01c675 100644
--- a/src/sink.rs
+++ b/src/sink.rs
@@ -311,11 +311,9 @@ where
 
         let partition_key = if self.get_config().print_key {
             let key = record_result.partition_key.to_string();
-            let key = self.write_key(&key);
-
-            format!("{} ", key)
+            Metadata::content(self.write_key(&key))
         } else {
-            "".to_string()
+            Metadata::Empty
         };
 
         let sequence_number = if self.get_config().print_sequence_number {
diff --git a/src/sink/console_tests.rs b/src/sink/console_tests.rs
index b9cf38b..2f51bd6 100644
--- a/src/sink/console_tests.rs
+++ b/src/sink/console_tests.rs
@@ -123,8 +123,7 @@ fn format_outputs_raw() {
     };
 
     let vec = console.format_record(&record);
-    let result = String::from_utf8_lossy(vec.as_slice());
-    assert_eq!(result, "Hello �World\n");
+    assert_eq!(vec, b"Hello \xF0\x90\x80World\n");
 }
 
 #[tokio::test]