diff --git a/sw/airborne/subsystems/datalink/telemetry.c b/sw/airborne/subsystems/datalink/telemetry.c
index f172d6105c..1bc2d62f71 100644
--- a/sw/airborne/subsystems/datalink/telemetry.c
+++ b/sw/airborne/subsystems/datalink/telemetry.c
@@ -35,7 +35,7 @@
  * @param _cb callback function, called according to telemetry mode and specified period
  * @return TRUE if message registered with success, FALSE otherwise
  */
-bool_t register_periodic_telemetry(struct pprz_telemetry * _pt, char * _msg, telemetry_cb _cb) {
+bool_t register_periodic_telemetry(struct pprz_telemetry * _pt, const char * _msg, telemetry_cb _cb) {
   // look for message name
   uint8_t i;
   for (i = 0; i < _pt->nb; i++) {
diff --git a/sw/airborne/subsystems/datalink/telemetry_common.h b/sw/airborne/subsystems/datalink/telemetry_common.h
index 30aaf3e0e0..96cf09dc46 100644
--- a/sw/airborne/subsystems/datalink/telemetry_common.h
+++ b/sw/airborne/subsystems/datalink/telemetry_common.h
@@ -58,7 +58,7 @@ struct pprz_telemetry {
  * @param _cb callback function, called according to telemetry mode and specified period
  * @return TRUE if message registered with success, FALSE otherwise
  */
-extern bool_t register_periodic_telemetry(struct pprz_telemetry * _pt, char * _msg, telemetry_cb _cb);
+extern bool_t register_periodic_telemetry(struct pprz_telemetry * _pt, const char * _msg, telemetry_cb _cb);
 
 #if USE_PERIODIC_TELEMETRY_REPORT
 /** Send an error report when trying to send message that as not been register
diff --git a/sw/include/std.h b/sw/include/std.h
index ca3cb52640..60a2ee85f0 100644
--- a/sw/include/std.h
+++ b/sw/include/std.h
@@ -239,10 +239,11 @@ typedef uint8_t unit_t;
     }									\
   }
 
-static inline bool_t str_equal(char * a, char * b) {
-  while (!(*a == 0 && *b == 0)) {
-    if (*a != *b) return FALSE;
-    a++; b++;
+static inline bool_t str_equal(const char * a, const char * b) {
+  int i = 0;
+  while (!(a[i] == 0 && b[i] == 0)) {
+    if (a[i] != b[i]) return FALSE;
+    i++;
   }
   return TRUE;
 }