diff --git a/lib/otp/otp.h b/lib/otp/otp.h
index 83f08c596..bddbf5b8f 100644
--- a/lib/otp/otp.h
+++ b/lib/otp/otp.h
@@ -42,6 +42,7 @@
 #define _OTP_H
 
 #include <stdlib.h>
+#include <time.h>
 
 enum {OTPKEYSIZE = 8};
 
@@ -76,6 +77,7 @@ typedef struct {
   char seed[17];
   OtpKey key;
   int challengep;
+  time_t lock_time;
   char *err;
 } OtpContext;