diff --git a/tools/blob_store_bench.cc b/tools/blob_store_bench.cc
index 6bedcb06f..70ece2c5f 100644
--- a/tools/blob_store_bench.cc
+++ b/tools/blob_store_bench.cc
@@ -11,7 +11,9 @@
 // BlobStore does costly asserts to make sure it's running correctly, which
 // significantly impacts benchmark runtime.
 // NDEBUG will compile out those asserts.
+#ifndef NDEBUG
 #define NDEBUG
+#endif
 
 using namespace rocksdb;
 using namespace std;