diff --git a/library/pem.c b/library/pem.c
index 3dd3b79..4e00b63 100644
--- a/library/pem.c
+++ b/library/pem.c
@@ -46,6 +46,11 @@
 
 #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;
+}
+
 #if defined(POLARSSL_PEM_PARSE_C)
 void pem_init( pem_context *ctx )
 {
@@ -99,8 +104,8 @@
     {
         memcpy( key, md5sum, keylen );
 
-        memset( &md5_ctx, 0, sizeof(  md5_ctx ) );
-        memset( md5sum, 0, 16 );
+        polarssl_zeroize( &md5_ctx, sizeof(  md5_ctx ) );
+        polarssl_zeroize( md5sum, 16 );
         return;
     }
 
@@ -121,8 +126,8 @@
 
     memcpy( key + 16, md5sum, use_len );
 
-    memset( &md5_ctx, 0, sizeof(  md5_ctx ) );
-    memset( md5sum, 0, 16 );
+    polarssl_zeroize( &md5_ctx, sizeof(  md5_ctx ) );
+    polarssl_zeroize( md5sum, 16 );
 }
 
 #if defined(POLARSSL_DES_C)
@@ -142,8 +147,8 @@
     des_crypt_cbc( &des_ctx, DES_DECRYPT, buflen,
                      des_iv, buf, buf );
 
-    memset( &des_ctx, 0, sizeof( des_ctx ) );
-    memset( des_key, 0, 8 );
+    polarssl_zeroize( &des_ctx, sizeof( des_ctx ) );
+    polarssl_zeroize( des_key, 8 );
 }
 
 /*
@@ -162,8 +167,8 @@
     des3_crypt_cbc( &des3_ctx, DES_DECRYPT, buflen,
                      des3_iv, buf, buf );
 
-    memset( &des3_ctx, 0, sizeof( des3_ctx ) );
-    memset( des3_key, 0, 24 );
+    polarssl_zeroize( &des3_ctx, sizeof( des3_ctx ) );
+    polarssl_zeroize( des3_key, 24 );
 }
 #endif /* POLARSSL_DES_C */
 
@@ -184,8 +189,8 @@
     aes_crypt_cbc( &aes_ctx, AES_DECRYPT, buflen,
                      aes_iv, buf, buf );
 
-    memset( &aes_ctx, 0, sizeof( aes_ctx ) );
-    memset( aes_key, 0, keylen );
+    polarssl_zeroize( &aes_ctx, sizeof( aes_ctx ) );
+    polarssl_zeroize( aes_key, keylen );
 }
 #endif /* POLARSSL_AES_C */
 
@@ -373,7 +378,7 @@
     polarssl_free( ctx->buf );
     polarssl_free( ctx->info );
 
-    memset( ctx, 0, sizeof( pem_context ) );
+    polarssl_zeroize( ctx, sizeof( pem_context ) );
 }
 #endif /* POLARSSL_PEM_PARSE_C */