diff --git a/src/Mod/Sketcher/App/ExternalGeometryExtension.h b/src/Mod/Sketcher/App/ExternalGeometryExtension.h
index 503c844951..4f3c1e6f68 100644
--- a/src/Mod/Sketcher/App/ExternalGeometryExtension.h
+++ b/src/Mod/Sketcher/App/ExternalGeometryExtension.h
@@ -43,7 +43,7 @@ public:
     };
     // END_CREDIT_BLOCK: Credit under LGPL for this block to Zheng, Lei (realthunder) <realthunder.dev@gmail.com>
 
-    constexpr static std::array<const char *,NumFlags> flag2str { "Defining", "Frozen", "Detached","Missing", "Sync" };
+    constexpr static std::array<const char *,NumFlags> flag2str {{ "Defining", "Frozen", "Detached","Missing", "Sync" }};
 
     ExternalGeometryExtension() = default;
     virtual ~ExternalGeometryExtension() = default;