diff --git a/src/ikarus.boot b/src/ikarus.boot
index 64de896..b04a456 100644
Binary files a/src/ikarus.boot and b/src/ikarus.boot differ
diff --git a/src/ikarus.bytevectors.ss b/src/ikarus.bytevectors.ss
index 464d682..d0d7728 100644
--- a/src/ikarus.bytevectors.ss
+++ b/src/ikarus.bytevectors.ss
@@ -5,8 +5,8 @@
           bytevector-copy! u8-list->bytevector bytevector->u8-list
           bytevector-u16-native-ref bytevector-u16-native-set!
           bytevector-u16-ref bytevector-u16-set!
-          bytevector-s16-native-ref
-          bytevector-s16-ref
+          bytevector-s16-native-ref bytevector-s16-native-set!
+          bytevector-s16-ref bytevector-s16-set!
           bytevector-fill! bytevector-copy bytevector=?
           bytevector-uint-ref bytevector-sint-ref 
           bytevector-uint-set!  bytevector-sint-set!
@@ -19,8 +19,8 @@
         bytevector-copy! u8-list->bytevector bytevector->u8-list
         bytevector-u16-native-ref bytevector-u16-native-set!
         bytevector-u16-ref bytevector-u16-set!
-        bytevector-s16-native-ref
-        bytevector-s16-ref
+        bytevector-s16-native-ref bytevector-s16-native-set!
+        bytevector-s16-ref bytevector-s16-set!
         bytevector-fill! bytevector-copy bytevector=?
         bytevector-uint-ref bytevector-sint-ref
         bytevector-uint-set!  bytevector-sint-set!
@@ -119,7 +119,7 @@
       (if (bytevector? x) 
           (if (and (fixnum? n) 
                    ($fx<= 0 n) 
-                   ($fx<= n (expt 2 16)))
+                   ($fx<= n #xFFFF))
               (if (and (fixnum? i)
                        ($fx<= 0 i)
                        ($fx< i ($fxsub1 ($bytevector-length x)))
@@ -131,6 +131,24 @@
               (error 'bytevector-u8-native-set! "invalid value ~s" n))
           (error 'bytevector-u16-native-set! "~s is not a bytevector" x))))
 
+
+  (define bytevector-s16-native-set!
+    (lambda (x i n) 
+      (if (bytevector? x) 
+          (if (and (fixnum? n) 
+                   ($fx<= #x-8000 n) 
+                   ($fx<= n #x7FFF))
+              (if (and (fixnum? i)
+                       ($fx<= 0 i)
+                       ($fx< i ($fxsub1 ($bytevector-length x)))
+                       ($fxzero? ($fxlogand i 1)))
+                  (begin
+                    ($bytevector-set! x i ($fxsra n 8)) 
+                    ($bytevector-set! x ($fxadd1 i) n))
+                  (error 'bytevector-s16-native-set! "invalid index ~s" i))
+              (error 'bytevector-s16-native-set! "invalid value ~s" n))
+          (error 'bytevector-s16-native-set! "~s is not a bytevector" x))))
+
   (define bytevector-s16-native-ref
     (lambda (x i) 
       (if (bytevector? x) 
@@ -203,6 +221,28 @@
               (error 'bytevector-s16-ref "invalid index ~s" i))
           (error 'bytevector-s16-ref "~s is not a bytevector" x))))
 
+
+  (define bytevector-s16-set!
+    (lambda (x i n end) 
+      (if (bytevector? x) 
+          (if (and (fixnum? n) 
+                   ($fx<= #x-8000 n) 
+                   ($fx<= n #x7FFF))
+              (if (and (fixnum? i)
+                       ($fx<= 0 i)
+                       ($fx< i ($fxsub1 ($bytevector-length x))))
+                  (case end
+                    [(big) 
+                     ($bytevector-set! x i ($fxsra n 8))
+                     ($bytevector-set! x ($fxadd1 i) n)]
+                    [(little) 
+                     ($bytevector-set! x i n)
+                     ($bytevector-set! x ($fxadd1 i) (fxsra n 8))]
+                    [else (error 'bytevector-s16-ref "invalid endianness ~s" end)])
+                  (error 'bytevector-s16-set! "invalid index ~s" i))
+              (error 'bytevector-s16-set! "invalid value ~s" n))
+          (error 'bytevector-s16-set! "~s is not a bytevector" x))))
+
   (define bytevector->u8-list
     (lambda (x)
       (unless (bytevector? x)
diff --git a/src/makefile.ss b/src/makefile.ss
index 5c31d31..2e7a32d 100755
--- a/src/makefile.ss
+++ b/src/makefile.ss
@@ -396,7 +396,9 @@
     [bytevector-u16-native-ref  i]
     [bytevector-u16-native-set! i]
     [bytevector-s16-ref         i]
+    [bytevector-s16-set!        i]
     [bytevector-s16-native-ref  i]
+    [bytevector-s16-native-set! i]
     [bytevector->u8-list     i]
     [u8-list->bytevector     i]
     [bytevector-copy!        i]
diff --git a/src/tests/bytevectors.ss b/src/tests/bytevectors.ss
index 8bab11c..11a82ac 100644
--- a/src/tests/bytevectors.ss
+++ b/src/tests/bytevectors.ss
@@ -210,6 +210,35 @@
        (bytevector-u16-set! v 0 12345 'big)
        (bytevector-u16-ref v 0 'big))]
 
+    [(lambda (x) (= x 12345))
+     (let ([v (make-bytevector 2)])
+       (bytevector-s16-native-set! v 0 12345)
+       (bytevector-s16-native-ref v 0))]
+    [(lambda (x) (= x 12345))
+     (let ([v (make-bytevector 2)])
+       (bytevector-s16-set! v 0 12345 'little)
+       (bytevector-s16-ref v 0 'little))]
+    [(lambda (x) (= x 12345))
+     (let ([v (make-bytevector 2)])
+       (bytevector-s16-set! v 0 12345 'big)
+       (bytevector-s16-ref v 0 'big))]
+
+    [(lambda (x) (= x -12345))
+     (let ([v (make-bytevector 2)])
+       (bytevector-s16-native-set! v 0 -12345)
+       (bytevector-s16-native-ref v 0))]
+    [(lambda (x) (= x -12345))
+     (let ([v (make-bytevector 2)])
+       (bytevector-s16-set! v 0 -12345 'little)
+       (bytevector-s16-ref v 0 'little))]
+    [(lambda (x) (= x -12345))
+     (let ([v (make-bytevector 2)])
+       (bytevector-s16-set! v 0 -12345 'big)
+       (bytevector-s16-ref v 0 'big))]
+
+
+
+
     ))
 
 
diff --git a/src/todo-r6rs.ss b/src/todo-r6rs.ss
index c68af99..81115c8 100755
--- a/src/todo-r6rs.ss
+++ b/src/todo-r6rs.ss
@@ -365,9 +365,9 @@
     [bytevector-ieee-single-ref                 S bv]
     [bytevector-length                          C bv]
     [bytevector-s16-native-ref                  C bv]
-    [bytevector-s16-native-set!                 S bv]
+    [bytevector-s16-native-set!                 C bv]
     [bytevector-s16-ref                         C bv]
-    [bytevector-s16-set!                        S bv]
+    [bytevector-s16-set!                        C bv]
     [bytevector-s32-native-ref                  S bv]
     [bytevector-s32-native-set!                 S bv]
     [bytevector-s32-ref                         S bv]
@@ -383,7 +383,7 @@
     [bytevector-u16-native-ref                  C bv]
     [bytevector-u16-native-set!                 C bv]
     [bytevector-u16-ref                         C bv]
-    [bytevector-u16-set!                        S bv]
+    [bytevector-u16-set!                        C bv]
     [bytevector-u32-native-ref                  S bv]
     [bytevector-u32-native-set!                 S bv]
     [bytevector-u32-ref                         S bv]