diff --git a/library/core/src/str/iter.rs b/library/core/src/str/iter.rs
index 8b952eab2946dd6865baf946bbc546ffd25554ff..83f484dc570c468d6b0a27b4c79dc79613871d74 100644
--- a/library/core/src/str/iter.rs
+++ b/library/core/src/str/iter.rs
@@ -47,12 +47,7 @@ fn next(&mut self) -> Option<char> {
     #[inline]
     fn count(self) -> usize {
         // length in `char` is equal to the number of non-continuation bytes
-        let bytes_len = self.iter.len();
-        let mut cont_bytes = 0;
-        for &byte in self.iter {
-            cont_bytes += utf8_is_cont_byte(byte) as usize;
-        }
-        bytes_len - cont_bytes
+        self.iter.filter(|&&byte| !utf8_is_cont_byte(byte)).count()
     }
 
     #[inline]