diff --git a/src/rtos/rtos.c b/src/rtos/rtos.c
index 8bfe3d5a7..87d23f98a 100644
--- a/src/rtos/rtos.c
+++ b/src/rtos/rtos.c
@@ -591,7 +591,7 @@ int rtos_get_gdb_reg(struct connection *connection, int reg_num)
 
 		free(reg_list);
 	}
-	return ERROR_FAIL;
+	return ERROR_NOT_IMPLEMENTED;
 }
 
 /** Return a list of general registers. */
diff --git a/src/server/gdb_server.c b/src/server/gdb_server.c
index 41a47bf3c..3d7a47af8 100644
--- a/src/server/gdb_server.c
+++ b/src/server/gdb_server.c
@@ -1397,8 +1397,13 @@ static int gdb_get_register_packet(struct connection *connection,
 	LOG_DEBUG("-");
 #endif
 
-	if ((target->rtos) && (rtos_get_gdb_reg(connection, reg_num) == ERROR_OK))
-		return ERROR_OK;
+	if (target->rtos) {
+		retval = rtos_get_gdb_reg(connection, reg_num);
+		if (retval == ERROR_OK)
+			return ERROR_OK;
+		if (retval != ERROR_NOT_IMPLEMENTED)
+			return gdb_error(connection, retval);
+	}
 
 	retval = target_get_gdb_reg_list_noread(target, &reg_list, &reg_list_size,
 			REG_CLASS_ALL);