diff --git a/collects/racket/list.rkt b/collects/racket/list.rkt
index b5e7a7282a..b5c8888049 100644
--- a/collects/racket/list.rkt
+++ b/collects/racket/list.rkt
@@ -157,7 +157,10 @@
 
 (define append*
   (case-lambda [(ls) (apply append ls)] ; optimize common case
-               [(l . lss) (apply append (apply list* l lss))]))
+               [(l1 l2) (apply append l1 l2)]
+               [(l1 l2 l3) (apply append l1 l2 l3)]
+               [(l1 l2 l3 l4) (apply append l1 l2 l3 l4)]
+               [(l . lss) (apply apply append l lss)]))
 
 (define (flatten orig-sexp)
   (let loop ([sexp orig-sexp] [acc null])
diff --git a/collects/racket/string.rkt b/collects/racket/string.rkt
index f09ee199a3..d1cee90a32 100644
--- a/collects/racket/string.rkt
+++ b/collects/racket/string.rkt
@@ -4,7 +4,11 @@
 
 (define string-append*
   (case-lambda [(strs) (apply string-append strs)] ; optimize common case
-               [(str . strss) (apply string-append (apply list* str strss))]))
+               [(s1 strs) (apply string-append s1 strs)]
+               [(s1 s2 strs) (apply string-append s1 s2 strs)]
+               [(s1 s2 s3 strs) (apply string-append s1 s2 s3 strs)]
+               [(s1 s2 s3 s4 strs) (apply string-append s1 s2 s3 s4 strs)]
+               [(str . strss) (apply apply string-append str strss)]))
 
 (require (only-in scheme/list add-between))