diff --git a/mediachanger/castorrmc/common/serror.c b/mediachanger/castorrmc/common/serror.c
index 47b194420e31ba4d91cdc1a5caead46145b2c747..9294580c40859e3267c21a78fc5d73722d65acb7 100644
--- a/mediachanger/castorrmc/common/serror.c
+++ b/mediachanger/castorrmc/common/serror.c
@@ -337,6 +337,7 @@ char *sys_terrlist[ETMAXERR-ETBASEOFF+2] =
    "Invalid tape-file sequence-number",
    "Invalid tape-file file-size",
    "Failed to mount tape",
+   "Failed to dismount tape",
    "BAD ERROR NUMBER"
   };
 
diff --git a/mediachanger/castorrmc/h/serrno.h b/mediachanger/castorrmc/h/serrno.h
index df2977fabdf27243a41da5a2e9cc3a532d311247..9b89f3d9364873255195fc24d58d554a41c5e216 100644
--- a/mediachanger/castorrmc/h/serrno.h
+++ b/mediachanger/castorrmc/h/serrno.h
@@ -342,7 +342,8 @@
 #define ETINVALIDTFSEQ	ETBASEOFF+39    /* Invalid tape-file sequence-number */
 #define ETINVALIDTFSIZE	ETBASEOFF+40    /* Invalid tape-file file-size */
 #define ETMOUNTFAILED	ETBASEOFF+41    /* Failed to mount tape */
-#define ETMAXERR        ETBASEOFF+41
+#define ETDISMOUNTFAILED ETBASEOFF+42   /* Failed to dismount tape */
+#define ETMAXERR        ETBASEOFF+42
 
 /*
  *------------------------------------------------------------------------