diff --git a/include/polarssl/ssl.h b/include/polarssl/ssl.h
index 4a01bbf4c8..3a0ac12d2a 100644
--- a/include/polarssl/ssl.h
+++ b/include/polarssl/ssl.h
@@ -2053,9 +2053,9 @@ int ssl_check_cert_usage( const x509_crt *cert,
 static inline int safer_memcmp( const void *a, const void *b, size_t n )
 {
     size_t i;
-    const unsigned char *A = (const unsigned char *) a;
-    const unsigned char *B = (const unsigned char *) b;
-    unsigned char diff = 0;
+    volatile const unsigned char *A = (volatile const unsigned char *) a;
+    volatile const unsigned char *B = (volatile const unsigned char *) b;
+    volatile unsigned char diff = 0;
 
     for( i = 0; i < n; i++ )
         diff |= A[i] ^ B[i];