diff --git a/cmd/collector/app/span_processor_test.go b/cmd/collector/app/span_processor_test.go
index d66383919a0..ff077713d93 100644
--- a/cmd/collector/app/span_processor_test.go
+++ b/cmd/collector/app/span_processor_test.go
@@ -25,6 +25,7 @@ import (
 	"time"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 	"go.uber.org/atomic"
 	"go.uber.org/zap"
 
@@ -291,11 +292,14 @@ func TestSpanProcessorErrors(t *testing.T) {
 
 type blockingWriter struct {
 	sync.Mutex
+	inWriteSpan atomic.Int32
 }
 
 func (w *blockingWriter) WriteSpan(ctx context.Context, span *model.Span) error {
+	w.inWriteSpan.Inc()
 	w.Lock()
 	defer w.Unlock()
+	w.inWriteSpan.Dec()
 	return nil
 }
 
@@ -666,18 +670,31 @@ func TestSpanProcessorWithOnDroppedSpanOption(t *testing.T) {
 		Options.NumWorkers(1),
 		Options.QueueSize(1),
 		Options.OnDroppedSpan(customOnDroppedSpan),
+		Options.ReportBusy(true),
 	).(*spanProcessor)
 	defer p.Close()
-	// block the writer so that the first span is read from the queue and blocks the processor, and followings are dropped.
+
+	// Acquire the lock externally to force the writer to block.
 	w.Lock()
 	defer w.Unlock()
 
+	opts := processor.SpansOptions{SpanFormat: processor.JaegerSpanFormat}
 	_, err := p.ProcessSpans([]*model.Span{
 		{OperationName: "op1"},
+	}, opts)
+	require.NoError(t, err)
+
+	// Wait for the sole worker to pick the item from the queue and block
+	assert.Eventually(t,
+		func() bool { return w.inWriteSpan.Load() == 1 },
+		time.Second, time.Microsecond)
+
+	// Now the queue is empty again and can accept one more item, but no workers available.
+	// If we send two items, the last one will have to be dropped.
+	_, err = p.ProcessSpans([]*model.Span{
 		{OperationName: "op2"},
 		{OperationName: "op3"},
-	}, processor.SpansOptions{SpanFormat: processor.JaegerSpanFormat})
-
-	assert.NoError(t, err)
-	assert.Equal(t, []string{"op2", "op3"}, droppedOperations)
+	}, opts)
+	assert.EqualError(t, err, processor.ErrBusy.Error())
+	assert.Equal(t, []string{"op3"}, droppedOperations)
 }