diff --git a/t/run/todo.t b/t/run/todo.t
index 1e6127e6d2..4754beea92 100644
--- a/t/run/todo.t
+++ b/t/run/todo.t
@@ -351,6 +351,16 @@ TODO: {
     isnt($?, 0, 'Compilation fails; GH 19378');
 }
 
+TODO: {
+    local $::TODO = 'GH 20491';
+    use experimental 'defer';
+    my $deferred = 0;
+    do {
+        defer { $deferred = 1 };
+    };
+    is($deferred, 1, 'defer in single-expression do block runs when exiting block; GH 20491');
+}
+
 TODO: {
     todo_skip 1 if is_miniperl();
     local $::TODO = 'GH 22168';