diff --git a/library/cipher.c b/library/cipher.c
index b48fd6d..5078d36 100644
--- a/library/cipher.c
+++ b/library/cipher.c
@@ -1159,7 +1159,7 @@
         }
 
         /* Check the tag in "constant-time" */
-        if( mbedtls_cf_memcmp( tag, check_tag, tag_len ) != 0 )
+        if( mbedtls_ct_memcmp( tag, check_tag, tag_len ) != 0 )
             return( MBEDTLS_ERR_CIPHER_AUTH_FAILED );
 
         return( 0 );
@@ -1181,7 +1181,7 @@
         }
 
         /* Check the tag in "constant-time" */
-        if( mbedtls_cf_memcmp( tag, check_tag, tag_len ) != 0 )
+        if( mbedtls_ct_memcmp( tag, check_tag, tag_len ) != 0 )
             return( MBEDTLS_ERR_CIPHER_AUTH_FAILED );
 
         return( 0 );