diff --git a/FU.pm b/FU.pm
index c178072..81bcf94 100644
--- a/FU.pm
+++ b/FU.pm
@@ -380,10 +380,11 @@ sub _do_req($c) {
         my($code, $msg) = ref $err eq 'FU::err' ? $err->@* : (500, $err);
         fu->reset;
         fu->status($code);
-        eval {
-            ($onerr{$code} || $onerr{500})->($code, $msg);
-            1;
-        } || _err_500();
+        my $ok = eval { ($onerr{$code} || $onerr{500})->($code, $msg) };
+        if (!$ok && !_is_done($@)) {
+            _log_err $@;
+            _err_500();
+        }
     }
 
     $REQ->{trace_end} = time;