diff --git a/user_guide.adoc b/user_guide.adoc
index 73d89ef..f8cf7b3 100644
--- a/user_guide.adoc
+++ b/user_guide.adoc
@@ -313,43 +313,67 @@ data — it all comes naturally from the `contents`.
 [[valid-values]]
 === Validating attribute values
 
-To ensure attributes in your data structures adhere to expected formats and ranges, Kaitai Struct provides a mechanism for validating attribute values using the `valid` key. This key allows you to define constraints for values, enhancing the robustness of your specifications. Here's how you can enforce these constraints:
+IMPORTANT: Feature available since v0.9.
 
-* `eq` (or directly `valid: value`): Ensures the attribute value exactly matches the given value.
-* `min`: Specifies the minimum valid value for the attribute.
-* `max`: Specifies the maximum valid value for the attribute.
-* `any-of`: Defines a list of acceptable values, one of which the attribute must match.
-* `expr`: An expression that evaluates to true for the attribute to be considered valid.
+To ensure attributes in your data structures adhere to expected formats
+and ranges, Kaitai Struct provides a mechanism for validating attribute
+values using the `valid` key. This key allows you to define constraints
+for values, enhancing the robustness of your specifications. Here's how
+you can enforce these constraints:
+
+* `eq` (or directly `valid: value`): ensures the attribute value exactly
+  matches the given value.
+* `min`: specifies the minimum valid value for the attribute.
+* `max`: specifies the maximum valid value for the attribute.
+* `any-of`: defines a list of acceptable values, one of which the
+  attribute must match.
+* `expr`: an expression that evaluates to true for the attribute to be
+  considered valid.
 
 For most cases, the direct `valid: value` shortcut is preferred for its simplicity, effectively functioning as `valid/eq`.
 
 [source,yaml]
 ----
 seq:
-  - id: exact_value
+  # Full form of equality constraint: the only valid value is 0x42
+  - id: exact_value1
+    type: u1
+    valid:
+      eq: 0x42
+
+  # Shortcut for the above: the only valid value is 0x42
+  - id: exact_value2
     type: u1
-    valid: 0x42  # Shortcut for eq: The only valid value is 0x42
+    valid: 0x42
 
+  # Value must be at least 100 and at most 200
   - id: bounded_value
     type: u2
     valid:
-      min: 100  # Value must be at least 100
-      max: 200  # and at most 200
+      min: 100
+      max: 200
 
-  - id: enum_value
+  # Value must be one of 3, 5, or 7
+  - id: enum_constraint_value
     type: u4
     valid:
-      any-of: [3, 5, 7]  # Value must be one of 3, 5, or 7
+      any-of: [3, 5, 7]
 
-  - id: calculated_value
+  # Value must be even
+  - id: expr_constraint_value
     type: u4
     valid:
-      expr: _ % 2 == 0  # Value must be even
+      expr: _ % 2 == 0
 ----
 
-When a value does not meet the specified criteria, Kaitai Struct raises a validation error, halting further parsing. This preemptive measure ensures the data being parsed is within the expected domain, providing a first layer of error handling.
+When a value does not meet the specified criteria, Kaitai Struct raises a
+validation error, halting further parsing. This preemptive measure
+ensures the data being parsed is within the expected domain, providing a
+first layer of error handling.
 
-NOTE: The actual implementation of validation checks is language-dependent and may vary in behavior and supported features across different target languages.
+NOTE: The actual implementation of validation checks is
+language-dependent and may vary in behavior and supported features across
+different target languages.
 
 [[var-length-struct]]
 === Variable-length structures