diff --git a/src/lex/lexer.l b/src/lex/lexer.l
index 8823195..c1efd4f 100644
--- a/src/lex/lexer.l
+++ b/src/lex/lexer.l
@@ -12,6 +12,9 @@
 %option nounput
 %option noinput
 
+/* prevent depency of unistd.h */
+%option nounistd
+
 %%
 "\n"    yyLineNumber++;