diff --git a/usr.bin/lex/flex.skl b/usr.bin/lex/flex.skl
index e894a272e06d..7cb7bcbf4707 100644
--- a/usr.bin/lex/flex.skl
+++ b/usr.bin/lex/flex.skl
@@ -26,7 +26,8 @@
 
 #include <stdlib.h>
 %+
-class istream;
+#include <iosfwd>
+using namespace std;
 %*
 #include <unistd.h>