diff --git a/_kiss_fft_guts.h b/_kiss_fft_guts.h
index 2018b65..147f398 100644
--- a/_kiss_fft_guts.h
+++ b/_kiss_fft_guts.h
@@ -37,17 +37,22 @@ struct kiss_fft_state{
    C_ADDTO( res , a)    : res += a
  * */
 #ifdef FIXED_POINT
-#   define S_MUL(a,b) ( ( (a)*(b) + (1<<14) )>>15 )
+
+#   define smul(a,b) ( (long)(a)*(b) )
+#   define sround( x )  (short)( ( (x) + (1<<14) ) >>15 )
+
+#   define S_MUL(a,b) sround( smul(a,b) )
+
 #   define C_MUL(m,a,b) \
-      do{ (m).r = ( ( (a).r*(b).r - (a).i*(b).i)  + (1<<14) ) >> 15;\
-          (m).i = ( ( (a).r*(b).i + (a).i*(b).r)  + (1<<14) ) >> 15;\
-      }while(0)
+      do{ (m).r = sround( smul((a).r,(b).r) - smul((a).i,(b).i) ); \
+          (m).i = sround( smul((a).r,(b).i) + smul((a).i,(b).r) ); }while(0)
+
 #   define C_FIXDIV(c,div) \
     do{ (c).r /= div; (c).i /=div; }while(0)
 
 #   define C_MULBYSCALAR( c, s ) \
-    do{ (c).r = ( ( (c).r*(s) ) + (1<<14) ) >> 15;\
-        (c).i = ( ( (c).i*(s) ) + (1<<14) ) >> 15; }while(0)
+    do{ (c).r =  sround( smul( (c).r , s ) ) ;\
+        (c).i =  sround( smul( (c).i , s ) ) ; }while(0)
 
 #else  /* not FIXED_POINT*/