diff --git a/library/hkdf.c b/library/hkdf.c
index d64dc4d..8157632 100644
--- a/library/hkdf.c
+++ b/library/hkdf.c
@@ -177,7 +177,7 @@
         }
 
         num_to_copy = i != n ? hash_len : okm_len - where;
-        memcpy( okm + where, t, num_to_copy );
+        mbedtls_platform_memcpy( okm + where, t, num_to_copy );
         where += hash_len;
         t_len = hash_len;
     }