diff --git a/_kiss_fft_guts.h b/_kiss_fft_guts.h
index afcbe1b..4bd8d1c 100644
--- a/_kiss_fft_guts.h
+++ b/_kiss_fft_guts.h
@@ -135,7 +135,7 @@ struct kiss_fft_state{
 #else
 #  define KISS_FFT_COS(phase) (kiss_fft_scalar) cos(phase)
 #  define KISS_FFT_SIN(phase) (kiss_fft_scalar) sin(phase)
-#  define HALF_OF(x) ((x)*.5)
+#  define HALF_OF(x) ((x)*((kiss_fft_scalar).5))
 #endif
 
 #define  kf_cexp(x,phase) \