diff --git a/src/lib/builtins/string.rs b/src/lib/builtins/string.rs
index 54090f52a0d..4b1343b80d2 100644
--- a/src/lib/builtins/string.rs
+++ b/src/lib/builtins/string.rs
@@ -744,18 +744,16 @@ pub fn replace(this: &Value, args: &[Value], ctx: &mut Interpreter) -> ResultVal
     let replacement = get_argument(args, 1);
     let replacement_str: &str = &ctx.value_to_rust_string(&replacement);
 
-    if pattern.is_string() {
-        let pattern_str: &str = &ctx.value_to_rust_string(&pattern);
-        // The Rust pattern is interpreted as a Regex and replaced in the original string with
-        // the replacement by using Regex.replace_all
-        let result_str = this_str.replace(pattern_str, replacement_str);
-        Ok(to_value(result_str))
-    } else {
-        pattern.with_internal_state_ref(|pattern_re: &RegExp| {
+    if let Some(re_internal_state) = pattern.get_internal_state() {
+        if let Some(pattern_re) = re_internal_state.downcast_ref::<RegExp>() {
             let result_str = pattern_re.replace_all(this_str, replacement_str);
-            Ok(to_value(result_str.into_owned()))
-        })
+            return Ok(to_value(result_str.into_owned()));
+        }
     }
+
+    let pattern_str: &str = &ctx.value_to_rust_string(&pattern);
+    let result_str = this_str.replace(pattern_str, replacement_str);
+    Ok(to_value(result_str))
 }
 
 fn get_argument(args: &[Value], idx: usize) -> Value {
@@ -1089,6 +1087,7 @@ mod tests {
         var result1 = str.replace('dog', 'monkey');
         var result2 = str.replace('dog.', 'monkey.');
         var regexResult = str.replace(/dog./, 'monkey.');
+        var intResult = 'abc4e'.replace(4, 'd')
         var exceptional1 = str.replace();
         var exceptional2 = str.replace('dog');
         "#;
@@ -1097,6 +1096,7 @@ mod tests {
         assert_eq!(forward(&mut engine, "result1"), "The quick brown fox jumps over the lazy monkey. If the monkey reacted, was it really lazy?");
         assert_eq!(forward(&mut engine, "result2"), "The quick brown fox jumps over the lazy monkey. If the dog reacted, was it really lazy?");
         assert_eq!(forward(&mut engine, "regexResult"), "The quick brown fox jumps over the lazy monkey. If the monkey.reacted, was it really lazy?");
+        assert_eq!(forward(&mut engine, "intResult"), "abcde");
         assert_eq!(
             forward(&mut engine, "exceptional1"),
             "The quick brown fox jumps over the lazy dog. If the dog reacted, was it really lazy?"