diff --git a/assembler/src/lex.l b/assembler/src/lex.l
index 31baca0e..17bb2339 100644
--- a/assembler/src/lex.l
+++ b/assembler/src/lex.l
@@ -1,5 +1,6 @@
 %option yylineno
 %{
+#include <string.h>
 #include "gen4asm.h"
 #include "gram.h"
 #include "brw_defines.h"