diff --git a/S17-supply/basic.t b/S17-supply/basic.t
index bf009ef931..6f388201e4 100644
--- a/S17-supply/basic.t
+++ b/S17-supply/basic.t
@@ -4,17 +4,24 @@ use lib $?FILE.IO.parent(2).add("packages");
 use Test;
 use Test::Util;
 
-plan 78;
+plan 80;
 
 for ThreadPoolScheduler.new, CurrentThreadScheduler -> $*SCHEDULER {
     diag "**** scheduling with {$*SCHEDULER.WHAT.perl}";
 
+    {
+        my $s = Supplier.new;
+        $s.Supply.tap( -> \val { ok val =:= Mu } );
+        $s.emit(Mu);
+        $s.done;
+    }
+
     {
         my $s = Supplier.new;
 
         my @vals;
         my $saw_done;
-        my $tap = $s.Supply.tap( -> $val { @vals.push($val) },
+        $s.Supply.tap( -> $val { @vals.push($val) },
           done => { $saw_done = True });
 
         $s.emit(1);