diff --git a/src/exec.rs b/src/exec.rs
index 431e35cf3..81bc490c2 100644
--- a/src/exec.rs
+++ b/src/exec.rs
@@ -965,11 +965,15 @@ fn function_restore_environment(parser: &Parser, block: BlockId) {
     Option<&mut OutputStream>,
 ) -> ProcStatus;
 
-// Return a function which may be to run the given process \p.
-// May return an empty std::function in the rare case that the to-be called fish function no longer
-// exists. This is just a dumb artifact of the fact that we only capture the functions name, not its
+// Return a function which may be to run the given process 'p'.
+// May return None in the rare case that the to-be called fish function no longer
+// exists. This is just an artifact of the fact that we only capture the functions name, not its
 // properties, when creating the job; thus a race could delete the function before we fetch its
-// properties.
+// properties. Note this is user visible. An example:
+//
+//    function foo; echo hi; end
+//    foo (functions --erase foo)
+//
 fn get_performer_for_process(
     p: &Process,
     job: &Job,
diff --git a/src/proc.rs b/src/proc.rs
index 15e18530c..d4aa5e46c 100644
--- a/src/proc.rs
+++ b/src/proc.rs
@@ -51,9 +51,12 @@ pub enum ProcessType {
     /// A regular external command.
     #[default]
     External,
-    /// A builtin command.
+    /// A builtin command. The builtin name is stored in `argv[0]`.
     Builtin,
     /// A shellscript function.
+    /// The function name is stored in `argv[0]`.
+    /// Note we don't capture the function body here, because the
+    /// function body may change as part of argument expansion.
     Function,
     /// A block of commands, represented as a node.
     /// This is always either block, ifs, or switchs, never boolean or decorated.
diff --git a/tests/checks/function.fish b/tests/checks/function.fish
index b1277dae6..2e30e08c7 100644
--- a/tests/checks/function.fish
+++ b/tests/checks/function.fish
@@ -174,4 +174,16 @@ functions -q foo
 echo exists $status
 # CHECK: exists 1
 
+# If a function is changed as part of its own arguments, then we see the change.
+# This codifies historic behavior.
+function foo; echo before; end
+foo (function foo; echo after; end)
+# CHECK: after
+
+# If a function is deleted as part of its own arguments, then we see the change.
+# This codifies historic behavior.
+function foo; echo before; end
+foo (functions --erase foo)
+# CHECKERR: error: Unknown function 'foo'
+
 exit 0