diff --git a/library/bignum.c b/library/bignum.c
index eb0fb51..5f61d13 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -39,6 +39,11 @@
 
 #include <stdlib.h>
 
+/* 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;
+}
+
 #define ciL    (sizeof(t_uint))         /* chars in limb  */
 #define biL    (ciL << 3)               /* bits  in limb  */
 #define biH    (ciL << 2)               /* half limb size */
@@ -72,7 +77,7 @@
 
     if( X->p != NULL )
     {
-        memset( X->p, 0, X->n * ciL );
+        polarssl_zeroize( X->p, X->n * ciL );
         free( X->p );
     }
 
@@ -101,7 +106,7 @@
         if( X->p != NULL )
         {
             memcpy( p, X->p, X->n * ciL );
-            memset( X->p, 0, X->n * ciL );
+            polarssl_zeroize( X->p, X->n * ciL );
             free( X->p );
         }