diff --git a/sql/sql_explain.cc b/sql/sql_explain.cc
index 8ded81788a2..70b177a556d 100644
--- a/sql/sql_explain.cc
+++ b/sql/sql_explain.cc
@@ -444,7 +444,8 @@ uint Explain_union::make_union_table_name(char *buf)
       break;
     default:
       DBUG_ASSERT(0);
-      type= {NULL, 0};
+      type.str= NULL;
+      type.length= 0;
   }
   memcpy(buf, type.str, (len= (uint)type.length));