diff --git a/kiss_fft.c b/kiss_fft.c
index af2f695..c64919b 100644
--- a/kiss_fft.c
+++ b/kiss_fft.c
@@ -349,8 +349,7 @@ kiss_fft_cfg kiss_fft_alloc(int nfft,int inverse_fft,void * mem,size_t * lenmem
         st->inverse = inverse_fft;
 
         for (i=0;i<nfft;++i) {
-            const double pi=3.141592653589793238462643383279502884197169399375105820974944;
-            double phase = -2*pi*i / nfft;
+            double phase = -2*kiss_fft_pi*i / nfft;
             if (st->inverse)
                 phase *= -1;
             kf_cexp(st->twiddles+i, phase );
diff --git a/kiss_fft.h b/kiss_fft.h
index 1ca0b45..040918a 100644
--- a/kiss_fft.h
+++ b/kiss_fft.h
@@ -56,6 +56,10 @@ extern "C" {
 # endif
 #endif
 
+#ifndef kiss_fft_pi
+#define kiss_fft_pi 3.141592653589793238462643383279502884197169399375105820974944
+#endif
+
 typedef struct {
     kiss_fft_scalar r;
     kiss_fft_scalar i;
diff --git a/tools/kiss_fftr.c b/tools/kiss_fftr.c
index 8102132..a2a8618 100644
--- a/tools/kiss_fftr.c
+++ b/tools/kiss_fftr.c
@@ -50,7 +50,7 @@ kiss_fftr_cfg kiss_fftr_alloc(int nfft,int inverse_fft,void * mem,size_t * lenme
 
     for (i = 0; i < nfft/2; ++i) {
         double phase =
-            -3.14159265358979323846264338327 * ((double) (i+1) / nfft + .5);
+            -kiss_fft_pi * ((double) (i+1) / nfft + .5);
         if (inverse_fft)
             phase *= -1;
         kf_cexp (st->super_twiddles+i,phase);