diff --git a/library/alloc/src/string.rs b/library/alloc/src/string.rs
index 906b0187f7bab..4f926d99c6dbc 100644
--- a/library/alloc/src/string.rs
+++ b/library/alloc/src/string.rs
@@ -558,13 +558,13 @@ impl String {
     pub fn from_utf8_lossy(v: &[u8]) -> Cow<'_, str> {
         let mut iter = lossy::Utf8Lossy::from_bytes(v).chunks();
 
-        let (first_valid, first_broken) = if let Some(chunk) = iter.next() {
+        let first_valid = if let Some(chunk) = iter.next() {
             let lossy::Utf8LossyChunk { valid, broken } = chunk;
-            if valid.len() == v.len() {
-                debug_assert!(broken.is_empty());
+            if broken.is_empty() {
+                debug_assert_eq!(valid.len(), v.len());
                 return Cow::Borrowed(valid);
             }
-            (valid, broken)
+            valid
         } else {
             return Cow::Borrowed("");
         };
@@ -573,9 +573,7 @@ impl String {
 
         let mut res = String::with_capacity(v.len());
         res.push_str(first_valid);
-        if !first_broken.is_empty() {
-            res.push_str(REPLACEMENT);
-        }
+        res.push_str(REPLACEMENT);
 
         for lossy::Utf8LossyChunk { valid, broken } in iter {
             res.push_str(valid);