diff --git a/library/x509.c b/library/x509.c
index d570f71..1e61db8 100644
--- a/library/x509.c
+++ b/library/x509.c
@@ -500,7 +500,7 @@
 {
     if( a->tag == b->tag &&
         a->len == b->len &&
-        memcmp( a->p, b->p, b->len ) == 0 )
+        mbedtls_platform_memcmp( a->p, b->p, b->len ) == 0 )
     {
         return( 0 );
     }
@@ -589,7 +589,7 @@
             goto exit;
 
         if( oid[0].len != oid[1].len ||
-            memcmp( oid[0].p, oid[1].p, oid[1].len ) != 0 )
+            mbedtls_platform_memcmp( oid[0].p, oid[1].p, oid[1].len ) != 0 )
         {
             return( 1 );
         }