diff --git a/real_data_benchmark_test.go b/real_data_benchmark_test.go
index b07b7fd7..7e47a323 100644
--- a/real_data_benchmark_test.go
+++ b/real_data_benchmark_test.go
@@ -12,6 +12,8 @@ import (
 	"testing"
 )
 
+// To run these benchmarks, type BENCH_REAL_DATA=1 go test -bench BenchmarkRealData -run -
+
 var benchRealData = false
 
 var realDatasets = []string{