diff --git a/starlette/middleware/errors.py b/starlette/middleware/errors.py
index 1f2c40b4..a3fe4f35 100644
--- a/starlette/middleware/errors.py
+++ b/starlette/middleware/errors.py
@@ -222,7 +222,7 @@ class ServerErrorMiddleware:
             exc_html += self.generate_frame_html(frame, center_lineno, is_collapsed)
             is_collapsed = True
 
-        error = f"{traceback_obj.exc_type.__name__}: {html.escape(traceback_obj)}"
+        error = f"{traceback_obj.exc_type.__name__}: {html.escape(str(traceback_obj))}"
 
         return TEMPLATE.format(styles=STYLES, js=JS, error=error, exc_html=exc_html)