diff --git a/libavcodec/h263.h b/libavcodec/h263.h
index 70fd1ffdc0..d6bef8318d 100644
--- a/libavcodec/h263.h
+++ b/libavcodec/h263.h
@@ -100,15 +100,16 @@ void ff_h263_encode_motion(PutBitContext *pb, int val, int f_code);
 
 
 static inline int h263_get_motion_length(int val, int f_code){
-    int l, bit_size, code;
+    int bit_size, code, sign;
 
     if (val == 0) {
         return 1; /* ff_mvtab[0][1] */
     } else {
         bit_size = f_code - 1;
         /* modulo encoding */
-        l= INT_BIT - 6 - bit_size;
-        val = (val<<l)>>l;
+        val  = sign_extend(val, 6 + bit_size);
+        sign = val >> 31;
+        val  = (val ^ sign) - sign; /* val = FFABS(val) */
         val--;
         code = (val >> bit_size) + 1;