diff --git a/include/mysql/plugin.h b/include/mysql/plugin.h
index d9aef6ac11c..87efbefde68 100644
--- a/include/mysql/plugin.h
+++ b/include/mysql/plugin.h
@@ -44,7 +44,8 @@ class THD;
 class Item;
 #define MYSQL_THD THD*
 #else
-#define MYSQL_THD void*
+struct THD;
+typedef struct THD* MYSQL_THD;
 #endif
 
 typedef char my_bool;
diff --git a/include/mysql/service_debug_sync.h b/include/mysql/service_debug_sync.h
index 0bd49a13458..f7fdbf04832 100644
--- a/include/mysql/service_debug_sync.h
+++ b/include/mysql/service_debug_sync.h
@@ -351,7 +351,11 @@ extern void (*debug_sync_C_callback_ptr)(MYSQL_THD, const char *, size_t);
 #endif /* defined(ENABLED_DEBUG_SYNC) */
 
 /* compatibility macro */
+#ifdef __cplusplus
+#define DEBUG_SYNC_C(name) DEBUG_SYNC(nullptr, name)
+#else
 #define DEBUG_SYNC_C(name) DEBUG_SYNC(NULL, name)
+#endif
 
 #ifdef __cplusplus
 }