diff --git a/src/include/taler_crypto_lib.h b/src/include/taler_crypto_lib.h
index 882b846a3..4e6eb4312 100644
--- a/src/include/taler_crypto_lib.h
+++ b/src/include/taler_crypto_lib.h
@@ -47,6 +47,8 @@
  */
 #define TALER_CNC_KAPPA 3
 
+#define TALER_CNC_KAPPA_MINUS_ONE_STR "2"
+
 
 /* ****************** Coin crypto primitives ************* */