ERROR_CHILD_MUST_BE_VOLATILE - 1021 (0x3FD)
Cannot create a stable subkey under a volatile parent key.
Updated: Feb 21, 2026
Technical Meaning
This error code indicates that a stable subkey cannot be created under a volatile parent key. A volatile key is one that is not persisted across system restarts, while a stable key remains intact.
Error Details
The error ERROR_CHILD_MUST_BE_VOLATILE (1021 or 0x3FD) is returned when an attempt is made to create a subkey under a parent key that is marked as volatile. This operation is not allowed because the volatile nature of the parent key implies that any changes made to its children will be lost upon system restart.
Usage Context
This error typically occurs during operations involving the Windows Registry, specifically when attempting to modify or create keys in a way that violates the volatile/stable key hierarchy rules. The registry is structured such that certain types of keys are intended for temporary data storage and should not have stable subkeys.
Developer Interpretation
Developers must ensure that they correctly identify and handle volatile vs. stable keys when performing operations on the Windows Registry. Violating these rules can lead to unexpected behavior or errors, as demonstrated by this specific error code.
Related Errors
ERROR_INVALID_KEY_NAME(193)ERROR_REGISTRY_QUOTA_LIMIT(2560)ERROR_CANT_ACCESS_DOMAIN_INFO(1784)
FAQ
Q: What does the ERROR_CHILD_MUST_BE_VOLATILE error mean?
A: This error indicates that a stable subkey cannot be created under a volatile parent key, as the volatile nature of the parent key implies that any changes made to its children will be lost upon system restart.
Q: How can I avoid this error?
A: Ensure that you correctly identify and handle volatile vs. stable keys when performing operations on the Windows Registry. Violating these rules can lead to unexpected behavior or errors, as demonstrated by this specific error code.
Summary
The ERROR_CHILD_MUST_BE_VOLATILE error (1021) is a specific technical issue related to the Windows Registry, where attempting to create a stable subkey under a volatile parent key results in an error. Developers must be mindful of the volatile/stable key hierarchy rules to avoid this and other similar errors.