diff --git a/askama_parser/src/expr.rs b/askama_parser/src/expr.rs
index 3e63d9306..7f822668b 100644
--- a/askama_parser/src/expr.rs
+++ b/askama_parser/src/expr.rs
@@ -254,7 +254,7 @@ impl<'a> Suffix<'a> {
             let mut in_str = false;
             let mut escaped = false;
 
-            for (i, c) in input.chars().enumerate() {
+            for (i, c) in input.char_indices() {
                 if !(c == '(' || c == ')') || !in_str {
                     match c {
                         '(' => nested += 1,
diff --git a/askama_parser/src/tests.rs b/askama_parser/src/tests.rs
index ce300d36a..c23d13f69 100644
--- a/askama_parser/src/tests.rs
+++ b/askama_parser/src/tests.rs
@@ -788,3 +788,10 @@ fn test_parse_array() {
         )],
     );
 }
+
+#[test]
+fn fuzzed_unicode_slice() {
+    let d = "{eeuuu{b&{!!&{!!11{{
+            0!(!1q҄א!)!!!!!!n!";
+    assert!(Ast::from_str(d, &Syntax::default()).is_err());
+}