diff --git a/library/pkparse.c b/library/pkparse.c
index 3c8063f..29217a2 100644
--- a/library/pkparse.c
+++ b/library/pkparse.c
@@ -62,12 +62,12 @@
 #define polarssl_free       free
 #endif
 
+#if defined(POLARSSL_FS_IO)
 /* 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_FS_IO)
 /*
  * Load all data from a file into a given buffer.
  */