diff --git a/library/sha4.c b/library/sha4.c
index 50987be..ebdc997 100644
--- a/library/sha4.c
+++ b/library/sha4.c
@@ -35,13 +35,13 @@
 #include <stdio.h>
 #endif
 
+#if !defined(POLARSSL_SHA4_ALT)
+
 /* Implementation that should never be optimized out by the compiler */
 static void polarssl_zeroize( void *v, size_t n ) {
     volatile unsigned char *p = v; while( n-- ) *p++ = 0;
 }
 
-#if !defined(POLARSSL_SHA4_ALT)
-
 /*
  * 64-bit integer manipulation macros (big endian)
  */