diff --git a/common_x86_64.h b/common_x86_64.h
index c05998d58..fe5539abe 100644
--- a/common_x86_64.h
+++ b/common_x86_64.h
@@ -225,7 +225,11 @@ static __inline int blas_quickdivide(unsigned int x, unsigned int y){
 #endif
 #define HUGE_PAGESIZE	( 2 << 20)
 
+#ifndef BUFFERSIZE
 #define BUFFER_SIZE	(32 << 20)
+#else
+#define BUFFER_SIZE	(32 << BUFFERSIZE)
+#endif
 
 #define SEEK_ADDRESS