diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index a700a079a218..58924eb0f40b 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -164,8 +164,8 @@ LN      = ln -f
 MKDIR   = mkdir
 FIND    = find
 INSTALL = install
-FLEX    = flex
-BISON   = bison
+FLEX    ?= flex
+BISON   ?= bison
 STRIP   = strip
 AWK     = awk