diff --git a/library/x509_csr.c b/library/x509_csr.c
index 529e7e4..d82679d 100644
--- a/library/x509_csr.c
+++ b/library/x509_csr.c
@@ -62,6 +62,11 @@
 #include <stdio.h>
 #endif
 
+/* 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;
+}
+
 /*
  *  Version  ::=  INTEGER  {  v1(0)  }
  */
@@ -295,7 +300,7 @@
 
     ret = x509_csr_parse( csr, buf, n );
 
-    memset( buf, 0, n + 1 );
+    polarssl_zeroize( buf, n + 1 );
     polarssl_free( buf );
 
     return( ret );
@@ -429,17 +434,17 @@
     {
         name_prv = name_cur;
         name_cur = name_cur->next;
-        memset( name_prv, 0, sizeof( x509_name ) );
+        polarssl_zeroize( name_prv, sizeof( x509_name ) );
         polarssl_free( name_prv );
     }
 
     if( csr->raw.p != NULL )
     {
-        memset( csr->raw.p, 0, csr->raw.len );
+        polarssl_zeroize( csr->raw.p, csr->raw.len );
         polarssl_free( csr->raw.p );
     }
 
-    memset( csr, 0, sizeof( x509_csr ) );
+    polarssl_zeroize( csr, sizeof( x509_csr ) );
 }
 
 #endif /* POLARSSL_X509_CSR_PARSE_C */