diff --git a/library/cmac.c b/library/cmac.c
index 3cc49d10c..987085686 100644
--- a/library/cmac.c
+++ b/library/cmac.c
@@ -148,15 +148,6 @@ exit:
 #endif /* !defined(MBEDTLS_CMAC_ALT) || defined(MBEDTLS_SELF_TEST) */
 
 #if !defined(MBEDTLS_CMAC_ALT)
-static void cmac_xor_block( unsigned char *output, const unsigned char *input1,
-                            const unsigned char *input2,
-                            const size_t block_size )
-{
-    size_t idx;
-
-    for( idx = 0; idx < block_size; idx++ )
-        output[ idx ] = input1[ idx ] ^ input2[ idx ];
-}
 
 /*
  * Create padded last block from (partial) last block.
@@ -247,7 +238,7 @@ int mbedtls_cipher_cmac_update( mbedtls_cipher_context_t *ctx,
                 input,
                 block_size - cmac_ctx->unprocessed_len );
 
-        cmac_xor_block( state, cmac_ctx->unprocessed_block, state, block_size );
+        mbedtls_xor( state, cmac_ctx->unprocessed_block, state, block_size );
 
         if( ( ret = mbedtls_cipher_update( ctx, state, block_size, state,
                                            &olen ) ) != 0 )
@@ -267,7 +258,7 @@ int mbedtls_cipher_cmac_update( mbedtls_cipher_context_t *ctx,
      * final partial or complete block */
     for( j = 1; j < n; j++ )
     {
-        cmac_xor_block( state, input, state, block_size );
+        mbedtls_xor( state, input, state, block_size );
 
         if( ( ret = mbedtls_cipher_update( ctx, state, block_size, state,
                                            &olen ) ) != 0 )
@@ -319,16 +310,16 @@ int mbedtls_cipher_cmac_finish( mbedtls_cipher_context_t *ctx,
     if( cmac_ctx->unprocessed_len < block_size )
     {
         cmac_pad( M_last, block_size, last_block, cmac_ctx->unprocessed_len );
-        cmac_xor_block( M_last, M_last, K2, block_size );
+        mbedtls_xor( M_last, M_last, K2, block_size );
     }
     else
     {
         /* Last block is complete block */
-        cmac_xor_block( M_last, last_block, K1, block_size );
+        mbedtls_xor( M_last, last_block, K1, block_size );
     }
 
 
-    cmac_xor_block( state, M_last, state, block_size );
+    mbedtls_xor( state, M_last, state, block_size );
     if( ( ret = mbedtls_cipher_update( ctx, state, block_size, state,
                                        &olen ) ) != 0 )
     {