diff --git a/circle.yml b/circle.yml
index 2a8fd41..051180e 100644
--- a/circle.yml
+++ b/circle.yml
@@ -54,13 +54,16 @@ jobs:
       - run:
           name: "Test documentation"
           command: |
-            doxygen Doxyfile > doxygen.log 2> doxygen.warnings
+            cat Doxyfile | sed 's/HTML_OUTPUT            = ./HTML_OUTPUT            = ..\/docs/' | doxygen - > doxygen.log 2> doxygen.warnings
             if [ -s doxygen.warnings ]; then
               printf '\n\nDoxygen warnings:\n\n'
               cat doxygen.warnings
               exit 1
             fi
             cat doxygen.log
+      - store_artifacts:
+          path: ~/docs
+          destination: docs
 
   upload-docs:
     docker:
diff --git a/include/evmc/evmc.h b/include/evmc/evmc.h
index c6ef635..dadcbfd 100644
--- a/include/evmc/evmc.h
+++ b/include/evmc/evmc.h
@@ -393,40 +393,6 @@ struct evmc_result
 };
 
 
-/**
- * The union representing evmc_result "optional data".
- *
- *  The evmc_result struct contains 24 bytes of optional data that can be
- *  reused by the object creator if the object does not contain
- *  evmc_result::create_address.
- *
- *  An EVM implementation MAY use this memory to keep additional data
- *  when returning result from ::evmc_execute_fn.
- *  The host application MAY use this memory to keep additional data
- *  when returning result of performed calls from ::evmc_call_fn.
- *
- *  @see evmc_get_optional_data(), evmc_get_const_optional_data().
- */
-union evmc_result_optional_data
-{
-    uint8_t bytes[24]; /**< 24 bytes of optional data. */
-    void* pointer;     /**< Optional pointer. */
-};
-
-/** Provides read-write access to evmc_result "optional data". */
-static inline union evmc_result_optional_data* evmc_get_optional_data(struct evmc_result* result)
-{
-    return (union evmc_result_optional_data*)&result->create_address;
-}
-
-/** Provides read-only access to evmc_result "optional data". */
-static inline const union evmc_result_optional_data* evmc_get_const_optional_data(
-    const struct evmc_result* result)
-{
-    return (const union evmc_result_optional_data*)&result->create_address;
-}
-
-
 /**
  * Check account existence callback function
  *
diff --git a/include/evmc/helpers.h b/include/evmc/helpers.h
index 66c7907..321da2c 100644
--- a/include/evmc/helpers.h
+++ b/include/evmc/helpers.h
@@ -51,4 +51,53 @@ static inline void evmc_release_result(struct evmc_result* result)
     result->release(result);
 }
 
+
+/**
+ * Helpers for optional storage of evmc_result.
+ *
+ * In some contexts (i.e. evmc_result::create_address is unused) objects of
+ * type evmc_result contains a memory storage that MAY be used by the object
+ * owner. This group defines helper types and functions for accessing
+ * the optional storage.
+ *
+ * @defgroup result_optional_storage Result Optional Storage
+ * @{
+ */
+
+/**
+ * The union representing evmc_result "optional storage".
+ *
+ * The evmc_result struct contains 24 bytes of optional storage that can be
+ * reused by the object creator if the object does not contain
+ * evmc_result::create_address.
+ *
+ * A VM implementation MAY use this memory to keep additional data
+ * when returning result from evmc_execute_fn().
+ * The host application MAY use this memory to keep additional data
+ * when returning result of performed calls from evmc_call_fn().
+ *
+ * @see evmc_get_optional_storage(), evmc_get_const_optional_storage().
+ */
+union evmc_result_optional_storage
+{
+    uint8_t bytes[24]; /**< 24 bytes of optional storage. */
+    void* pointer;     /**< Optional pointer. */
+};
+
+/** Provides read-write access to evmc_result "optional storage". */
+static inline union evmc_result_optional_storage* evmc_get_optional_storage(
+    struct evmc_result* result)
+{
+    return (union evmc_result_optional_storage*)&result->create_address;
+}
+
+/** Provides read-only access to evmc_result "optional storage". */
+static inline const union evmc_result_optional_storage* evmc_get_const_optional_storage(
+    const struct evmc_result* result)
+{
+    return (const union evmc_result_optional_storage*)&result->create_address;
+}
+
+/** @} */
+
 /** @} */
diff --git a/test/vmtester/tests.cpp b/test/vmtester/tests.cpp
index 178afc2..1009249 100644
--- a/test/vmtester/tests.cpp
+++ b/test/vmtester/tests.cpp
@@ -4,6 +4,8 @@
 
 #include "vmtester.hpp"
 
+#include <evmc/helpers.h>
+
 #include <cstring>
 
 // Compile time checks:
@@ -22,7 +24,7 @@ static_assert(sizeof(evmc_revision) == sizeof(int), "Enum `evmc_revision` is not
 
 static constexpr size_t optionalDataSize =
     sizeof(evmc_result) - offsetof(evmc_result, create_address);
-static_assert(optionalDataSize == sizeof(evmc_result_optional_data), "");
+static_assert(optionalDataSize == sizeof(evmc_result_optional_storage), "");
 
 TEST_F(evmc_vm_test, abi_version_match)
 {