diff --git a/conformance-tests/2023-09/base/job_templates/3.5--env-script-onexit-only.invalid.yaml b/conformance-tests/2023-09/base/job_templates/3.5--env-script-onexit-only.yaml
similarity index 100%
rename from conformance-tests/2023-09/base/job_templates/3.5--env-script-onexit-only.invalid.yaml
rename to conformance-tests/2023-09/base/job_templates/3.5--env-script-onexit-only.yaml
diff --git a/rfcs/0008-environment-wrap-actions.md b/rfcs/0008-environment-wrap-actions.md
index fb275724..6df68e0a 100644
--- a/rfcs/0008-environment-wrap-actions.md
+++ b/rfcs/0008-environment-wrap-actions.md
@@ -280,7 +280,8 @@ The following terms are used throughout this specification.
 
 ```diff
   <EnvironmentActions> ::= the object:
-    onEnter: <Action>
+-   onEnter: <Action>
++   onEnter: <Action> # @optional
 +   onWrapEnvEnter: <Action>    # @optional @extension WRAP_ACTIONS
 +   onWrapTaskRun: <Action>     # @optional @extension WRAP_ACTIONS
 +   onWrapEnvExit: <Action>     # @optional @extension WRAP_ACTIONS
@@ -297,6 +298,10 @@ The following terms are used throughout this specification.
    *inner* environment that exits while this environment is active.
 5. *onExit*: the action to run when exiting the environment.
 
+At least one of *onEnter* or *onExit* must be provided. Defining a complete set
+of wrap hooks (subject to the all-or-nothing rule below) also satisfies this
+requirement.
+
 Each wrap hook receives the wrapped action's context via the
 `WrappedAction.*` template variables (see
 [Template variables](#template-variables)).
diff --git a/wiki/2023-09-Template-Schemas.md b/wiki/2023-09-Template-Schemas.md
index 43e082b4..2cd3441d 100644
--- a/wiki/2023-09-Template-Schemas.md
+++ b/wiki/2023-09-Template-Schemas.md
@@ -1569,11 +1569,11 @@ embeddedFiles: [ <EmbeddedFile>, ... ] # @optional
 An `<EnvironmentActions>` is the object:
 
 ```yaml
-onEnter: <Action>
+onEnter: <Action> # @optional
 onWrapEnvEnter: <Action>    # @optional @extension WRAP_ACTIONS
 onWrapTaskRun: <Action>     # @optional @extension WRAP_ACTIONS
 onWrapEnvExit: <Action>     # @optional @extension WRAP_ACTIONS
-onExit: <Action> # optional
+onExit: <Action> # @optional
 ```
 
 1. *onEnter* — The action run when the environment is being entered on a host.
@@ -1591,6 +1591,9 @@ onExit: <Action> # optional
    reasonable default expectation should be that OpenJobDescription sessions are able to end and
    cleanup within a bound amount of time.
 
+Subject to the constraint that at least one of *onEnter* or *onExit* must be provided. (With the
+`WRAP_ACTIONS` extension, a complete set of wrap hooks also satisfies this requirement.)
+
 > **`WRAP_ACTIONS` extension constraints.**
 >
 > 1. *All-or-nothing rule.* An environment that defines any of `onWrapEnvEnter`, `onWrapTaskRun`, or