# ERROR: Cannot load message class for \[my\_examples\_pkg/Age\]. Are your messages built? Exercise 3.3

**URL:** <https://get-help.theconstruct.ai/t/error-cannot-load-message-class-for-my-examples-pkg-age-are-your-messages-built-exercise-3-3/5866>\
**Category:** ROS Basics In 5 Days (Python)\
**Tags:** error\
**Created:** [October 27, 2020, 5:07am UTC](https://get-help.theconstruct.ai/t/error-cannot-load-message-class-for-my-examples-pkg-age-are-your-messages-built-exercise-3-3/5866 "2020-10-27T05:07:18Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![akshay.ulavan](https://get-help.theconstruct.ai/letter_avatar_proxy/v4/letter/a/5f9b8f/32.png) [@akshay.ulavan](https://get-help.theconstruct.ai/u/akshay.ulavan)\
**Post date:** [October 27, 2020, 5:07am UTC](https://get-help.theconstruct.ai/t/error-cannot-load-message-class-for-my-examples-pkg-age-are-your-messages-built-exercise-3-3/5866/1 "2020-10-27T05:07:18Z")

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I’m trying to solve the exercise 3.3 where I have to create a publisher to publish age of robot using custom message format. I followed the instructions to create the Age.msg and aslo added the necessary lines to CMakeLists.txt and package.xml.  
When I start the node the topic can be seen in rostopic list and rostopic info as seen below.  
But when I try to echo the topic I get an error:

```
user:~$ rostopic info /age_info
Type: my_examples_pkg/Age

Publishers:
 * /publish_age_node (http://9_xterm:33941/)

Subscribers: None

user:~$ rostopic echo /age_info
ERROR: Cannot load message class for [my_examples_pkg/Age]. Are your messages built?
```

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**Author:** ![bayodesegun](https://get-help.theconstruct.ai/user_avatar/get-help.theconstruct.ai/bayodesegun/32/10684_2.png) [@bayodesegun](https://get-help.theconstruct.ai/u/bayodesegun)\
**Post date:** [October 27, 2020, 9:30am UTC](https://get-help.theconstruct.ai/t/error-cannot-load-message-class-for-my-examples-pkg-age-are-your-messages-built-exercise-3-3/5866/2 "2020-10-27T09:30:17Z")

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Hi @akshay.ulavan,

Welcome to the Community!

For solving this problem, please have a look at this post:

> **[ERROR: Cannot load message class for \[package/Message\]. Are your messages built?](https://get-help.theconstruct.ai/t/error-cannot-load-message-class-for-package-message-are-your-messages-built/55)**
>
> This error usually happens when you create a custom ROS message. SOLUTION: Please check the following in order. Painfully 🙂, #3 is a common and repeated cause, and it tends to happen even if you already know about it! Have you made the...

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<div class="post-metadata">

**Author:** ![akshay.ulavan](https://get-help.theconstruct.ai/letter_avatar_proxy/v4/letter/a/5f9b8f/32.png) [@akshay.ulavan](https://get-help.theconstruct.ai/u/akshay.ulavan)\
**Post date:** [October 27, 2020, 11:28am UTC](https://get-help.theconstruct.ai/t/error-cannot-load-message-class-for-my-examples-pkg-age-are-your-messages-built-exercise-3-3/5866/3 "2020-10-27T11:28:58Z")

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Thanks @bayodesegun I am really enjoying the course 😀

My issue was as mentioned in the post #3. I didn’t understand it the first time. But I realized that I hadn’t done source devel/setup.bash in shell 2 where I was running the command rostopic echo.

Thanks for the quick response!