diff --git a/lambda-runtime/src/layers/panic.rs b/lambda-runtime/src/layers/panic.rs
index 4b92e3c8..257a8f39 100644
--- a/lambda-runtime/src/layers/panic.rs
+++ b/lambda-runtime/src/layers/panic.rs
@@ -99,6 +99,8 @@ impl<F> CatchPanicFuture<'_, F> {
     fn build_panic_diagnostic(err: &Box<dyn Any + Send>) -> Diagnostic {
         let error_message = if let Some(msg) = err.downcast_ref::<&str>() {
             format!("Lambda panicked: {msg}")
+        } else if let Some(msg) = err.downcast_ref::<String>() {
+            format!("Lambda panicked: {msg}")
         } else {
             "Lambda panicked".to_string()
         };