diff --git a/fish-rust/src/builtins/function.rs b/fish-rust/src/builtins/function.rs
index 0f452c134..ec0b20338 100644
--- a/fish-rust/src/builtins/function.rs
+++ b/fish-rust/src/builtins/function.rs
@@ -156,7 +156,7 @@ fn parse_cmd_opts(
                     if pid.is_err() || pid.unwrap() < 0 {
                         streams
                             .err
-                            .append(wgettext_fmt!("%ls: %ls: invalid process id", cmd));
+                            .append(wgettext_fmt!("%ls: %ls: invalid process id", cmd, woptarg));
                         return STATUS_INVALID_ARGS;
                     }
                     let pid = pid.unwrap();
diff --git a/tests/checks/function.fish b/tests/checks/function.fish
index c4be11e71..e665e89ec 100644
--- a/tests/checks/function.fish
+++ b/tests/checks/function.fish
@@ -162,4 +162,9 @@ end
 
 rm -r $tmpdir
 
+function foo -p bar; end
+# CHECKERR: {{.*}}function.fish (line {{\d+}}): function: bar: invalid process id
+# CHECKERR: function foo -p bar; end
+# CHECKERR: ^~~~~~~~~~~~~~~~~~~^
+
 exit 0