diff --git a/include/ecrt.h b/include/ecrt.h
index 6c3406b5..7556be25 100644
--- a/include/ecrt.h
+++ b/include/ecrt.h
@@ -788,6 +788,8 @@ size_t ecrt_domain_size(
         ec_domain_t *domain /**< Domain. */
         );
 
+#ifdef __KERNEL__
+
 /** Provide external memory to store the domain's process data.
  *
  * Call this after all Pdo entries have been registered and before activating
@@ -802,6 +804,8 @@ void ecrt_domain_external_memory(
                           data in. */
         );
 
+#endif /* __KERNEL__ */
+
 /** Returns the domain's process data.
  *
  * If external memory was provided with ecrt_domain_external_memory(), the