diff --git a/library/poly1305.c b/library/poly1305.c
index 2b56c5f..6fd9044 100644
--- a/library/poly1305.c
+++ b/library/poly1305.c
@@ -404,7 +404,7 @@
         ctx->queue_len++;
 
         /* Pad with zeroes */
-        memset( &ctx->queue[ctx->queue_len],
+        mbedtls_platform_memset( &ctx->queue[ctx->queue_len],
                 0,
                 POLY1305_BLOCK_SIZE_BYTES - ctx->queue_len );