diff --git a/lib/c/2006/labcomm2006.c b/lib/c/2006/labcomm2006.c
index 8f628cfccd6b10dda2635577cfd6c150e7ec4625..ff09b636127ffd0746165b98db2b453d975bad96 100644
--- a/lib/c/2006/labcomm2006.c
+++ b/lib/c/2006/labcomm2006.c
@@ -237,7 +237,7 @@ void *labcomm2006_signature_array_ref(struct labcomm2006_memory *memory,
   }
 }
 
-static int local_index = 0x40;
+static int local_index = LABCOMM_USER;
 
 void labcomm2006_set_local_index(struct labcomm2006_signature *signature)
 {
diff --git a/lib/c/2006/labcomm2006_private.h b/lib/c/2006/labcomm2006_private.h
index 4c3361026bf8e3c83af75fcca44cdebec43453b5..378719ccd2f7eff21df847ffb37cc76ad3838ac9 100644
--- a/lib/c/2006/labcomm2006_private.h
+++ b/lib/c/2006/labcomm2006_private.h
@@ -42,7 +42,7 @@
 #define LABCOMM_SAMPLE   0x02
 #define LABCOMM_ARRAY    0x10
 #define LABCOMM_STRUCT   0x11
-#define LABCOMM_USER     0x80   /* ..0xffffffff */
+#define LABCOMM_USER     0x40   /* ..0xffffffff */
 
 /*
  * Predefined primitive type indices
diff --git a/lib/c/2014/labcomm.c b/lib/c/2014/labcomm.c
index c11f50b0c634abdb925b4f4697cec10820475df4..a01c96bd8018687e8e3356e50ad01c3025d50ba3 100644
--- a/lib/c/2014/labcomm.c
+++ b/lib/c/2014/labcomm.c
@@ -236,7 +236,7 @@ void *labcomm_signature_array_ref(struct labcomm_memory *memory,
   }
 }
 
-static int local_index = 0x40;
+static int local_index = LABCOMM_USER;
 
 void labcomm_set_local_index(struct labcomm_signature *signature)
 {