diff --git a/tools/perf/util/expr.y b/tools/perf/util/expr.y
index 6c93b358cc2d..e364790babb5 100644
--- a/tools/perf/util/expr.y
+++ b/tools/perf/util/expr.y
@@ -1,6 +1,8 @@
 /* Simple expression parser */
 %{
+#ifndef NDEBUG
 #define YYDEBUG 1
+#endif
 #include <assert.h>
 #include <math.h>
 #include <stdlib.h>