diff --git a/Build.md b/Build.md
index 0364395..c3b4c6d 100644
--- a/Build.md
+++ b/Build.md
@@ -1,7 +1,7 @@
 * CMake 3.1 or higher
 * C++ Compiler with C++17 support:
   * Clang 5 or higher
-  * GCC 6 or higher
+  * GCC 7 or higher (`optional,string_view` require libstdc++7 or higher)
   * MSVC 2017 or higher (included with VS2017 Build Tools)
 
 See [[Getting-started]] for simple cmake build instructions.