diff --git a/include/cryb/oath_types.h b/include/cryb/oath_types.h
index b01cd90..d9ad829 100644
--- a/include/cryb/oath_types.h
+++ b/include/cryb/oath_types.h
@@ -47,9 +47,11 @@ typedef struct {
 	oath_mode	 mode;
 	oath_hash	 hash;
 	unsigned int	 digits;
-	uint64_t	 counter;  /* HOTP only */
+	union {
+		uint64_t	 counter;  /* HOTP */
+		uint64_t	 lastused; /* TOTP */
+	};
 	unsigned int	 timestep; /* TOTP only - in seconds */
-	uint64_t	 lastused; /* TOTP only */
 
 	/* housekeeping */
 	unsigned int	 dummy:1;  /* dummy key, always fail */