diff --git a/src/modules/module_15400.c b/src/modules/module_15400.c
index 297bbc670..0660d13b6 100644
--- a/src/modules/module_15400.c
+++ b/src/modules/module_15400.c
@@ -53,6 +53,13 @@ typedef struct chacha20
 
 static const char *SIGNATURE_CHACHA20 = "$chacha20$";
 
+const char *module_benchmark_mask (MAYBE_UNUSED const hashconfig_t *hashconfig, MAYBE_UNUSED const user_options_t *user_options, MAYBE_UNUSED const user_options_extra_t *user_options_extra)
+{
+  const char *mask = "?a?a?a?a?a?a?a?axxxxxxxxxxxxxxxxxxxxxxxxx";
+
+  return mask;
+}
+
 u64 module_esalt_size (MAYBE_UNUSED const hashconfig_t *hashconfig, MAYBE_UNUSED const user_options_t *user_options, MAYBE_UNUSED const user_options_extra_t *user_options_extra)
 {
   const u64 esalt_size = (const u64) sizeof (chacha20_t);
@@ -208,7 +215,7 @@ void module_init (module_ctx_t *module_ctx)
   module_ctx->module_attack_exec              = module_attack_exec;
   module_ctx->module_benchmark_esalt          = MODULE_DEFAULT;
   module_ctx->module_benchmark_hook_salt      = MODULE_DEFAULT;
-  module_ctx->module_benchmark_mask           = MODULE_DEFAULT;
+  module_ctx->module_benchmark_mask           = module_benchmark_mask;
   module_ctx->module_benchmark_salt           = MODULE_DEFAULT;
   module_ctx->module_build_plain_postprocess  = MODULE_DEFAULT;
   module_ctx->module_deep_comp_kernel         = MODULE_DEFAULT;