diff --git a/clippy_lints/src/returns.rs b/clippy_lints/src/returns.rs
index 0b72c8a07192..77a954cff62b 100644
--- a/clippy_lints/src/returns.rs
+++ b/clippy_lints/src/returns.rs
@@ -465,8 +465,8 @@ fn last_statement_borrows<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>)
 // Go backwards while encountering whitespace and extend the given Span to that point.
 fn extend_span_to_previous_non_ws(cx: &LateContext<'_>, sp: Span) -> Span {
     if let Ok(prev_source) = cx.sess().source_map().span_to_prev_source(sp) {
-        let ws = [' ', '\t', '\n'];
-        if let Some(non_ws_pos) = prev_source.rfind(|c| !ws.contains(&c)) {
+        let ws = [b' ', b'\t', b'\n'];
+        if let Some(non_ws_pos) = prev_source.bytes().rposition(|c| !ws.contains(&c)) {
             let len = prev_source.len() - non_ws_pos - 1;
             return sp.with_lo(sp.lo() - BytePos::from_usize(len));
         }
diff --git a/tests/ui/crashes/ice-12491.fixed b/tests/ui/crashes/ice-12491.fixed
new file mode 100644
index 000000000000..4ea480b0663c
--- /dev/null
+++ b/tests/ui/crashes/ice-12491.fixed
@@ -0,0 +1,7 @@
+#![warn(clippy::needless_return)]
+
+fn main() {
+    if (true) {
+        // anything一些中文
+    }
+}
diff --git a/tests/ui/crashes/ice-12491.rs b/tests/ui/crashes/ice-12491.rs
new file mode 100644
index 000000000000..60add6afa2c4
--- /dev/null
+++ b/tests/ui/crashes/ice-12491.rs
@@ -0,0 +1,8 @@
+#![warn(clippy::needless_return)]
+
+fn main() {
+    if (true) {
+        // anything一些中文
+        return;
+    }
+}
diff --git a/tests/ui/crashes/ice-12491.stderr b/tests/ui/crashes/ice-12491.stderr
new file mode 100644
index 000000000000..7cc418898e88
--- /dev/null
+++ b/tests/ui/crashes/ice-12491.stderr
@@ -0,0 +1,19 @@
+error: unneeded `return` statement
+  --> tests/ui/crashes/ice-12491.rs:5:24
+   |
+LL |           // anything一些中文
+   |  ____________________________^
+LL | |         return;
+   | |______________^
+   |
+   = note: `-D clippy::needless-return` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::needless_return)]`
+help: remove `return`
+   |
+LL -         // anything一些中文
+LL -         return;
+LL +         // anything一些中文
+   |
+
+error: aborting due to 1 previous error
+