diff --git a/python/lsst/ctrl/mpexec/cli/opt/options.py b/python/lsst/ctrl/mpexec/cli/opt/options.py
index 51a1549a..813d6758 100644
--- a/python/lsst/ctrl/mpexec/cli/opt/options.py
+++ b/python/lsst/ctrl/mpexec/cli/opt/options.py
@@ -478,19 +478,25 @@ def parse_mock_failure(
     value : `~collections.abc.Iterable` [`str`] or `None`
         Value from option.
     """
+    from lsst.pipe.base.tests.mocks import ForcedFailure
+
     result: dict[str, tuple[str, type[Exception] | None]] = {}
     if value is None:
         return result
     for entry in value:
         try:
-            task_label, error_type_name, where = entry.split(":", 2)
+            task_label, error_type_name, where, *rest = entry.split(":")
+            if rest:
+                (memory_required,) = rest
+            else:
+                memory_required = None
         except ValueError:
             raise click.UsageError(
                 f"Invalid value for --mock-failure option: {entry!r}; "
-                "expected a string of the form 'task:error:where'."
+                "expected a string of the form 'task:error:where[:mem]'."
             ) from None
         error_type = doImportType(error_type_name) if error_type_name else None
-        result[task_label] = (where, error_type)
+        result[task_label] = ForcedFailure(where, error_type, memory_required)
     return result
 
 
@@ -502,11 +508,15 @@ def parse_mock_failure(
     multiple=True,
     help=unwrap(
         """Specifications for tasks that should be configured to fail
-        when mocking execution.  This is a colon-separated 3-tuple, where the
-        first entry the task label, the second the fully-qualified exception
-        type (empty for ValueError, and the third a string (which typically
-        needs to be quoted to be passed as one argument value by the shell) of
-        the form passed to --where, indicating which data IDs should fail."""
+        when mocking execution.  This is a colon-separated 3-tuple or 4-tuple,
+        where the first entry the task label, the second the fully-qualified
+        exception type (empty for ValueError, and the third a string (which
+        typically needs to be quoted to be passed as one argument value by the
+        shell) of the form passed to --where, indicating which data IDs should
+        fail.  The final optional term is a memory threshold (with units
+        recognized by astropy), which will cause the error to only occur if
+        the available memory (according to ExecutionResources.max_mem) is less
+        than this value."""
     ),
 )