diff --git a/library/sha1.c b/library/sha1.c
index 14331b3..ffad228 100644
--- a/library/sha1.c
+++ b/library/sha1.c
@@ -46,13 +46,13 @@
 #endif /* MBEDTLS_PLATFORM_C */
 #endif /* MBEDTLS_SELF_TEST */
 
+#if !defined(MBEDTLS_SHA1_ALT)
+
 /* Implementation that should never be optimized out by the compiler */
 static void mbedtls_zeroize( void *v, size_t n ) {
     volatile unsigned char *p = v; while( n-- ) *p++ = 0;
 }
 
-#if !defined(MBEDTLS_SHA1_ALT)
-
 /*
  * 32-bit integer manipulation macros (big endian)
  */