diff --git a/kiss_fft.h b/kiss_fft.h
index 1ca0b45..ed6e24a 100644
--- a/kiss_fft.h
+++ b/kiss_fft.h
@@ -31,15 +31,24 @@ extern "C" {
   in the tools/ directory.
 */
 
+/* User may override KISS_FFT_MALLOC and/or KISS_FFT_FREE. */
 #ifdef USE_SIMD
 # include <xmmintrin.h>
 # define kiss_fft_scalar __m128
-#define KISS_FFT_MALLOC(nbytes) _mm_malloc(nbytes,16)
-#define KISS_FFT_FREE _mm_free
-#else	
-#define KISS_FFT_MALLOC malloc
-#define KISS_FFT_FREE free
-#endif	
+# ifndef KISS_FFT_MALLOC
+#  define KISS_FFT_MALLOC(nbytes) _mm_malloc(nbytes,16)
+# endif
+# ifndef KISS_FFT_FREE
+#  define KISS_FFT_FREE _mm_free
+# endif
+#else
+# ifndef KISS_FFT_MALLOC
+#  define KISS_FFT_MALLOC malloc
+# endif
+# ifndef KISS_FFT_FREE
+#  define KISS_FFT_FREE free
+# endif
+#endif
 
 
 #ifdef FIXED_POINT