diff -up widelands-1.0/CMakeLists.txt~ widelands-1.0/CMakeLists.txt
--- widelands-1.0/CMakeLists.txt~	2021-06-14 11:22:20.000000000 +0200
+++ widelands-1.0/CMakeLists.txt	2022-03-04 17:22:38.799386008 +0100
@@ -314,9 +314,8 @@ if(NOT MSVC)
   wl_add_flag(WL_COMPILE_DIAGNOSTICS "-Werror=format-security")
   wl_add_flag(WL_COMPILE_DIAGNOSTICS "-Werror=return-type")
   wl_add_flag(WL_COMPILE_DIAGNOSTICS "-Werror=shadow")
-  wl_add_flag(WL_COMPILE_DIAGNOSTICS "-Werror=uninitialized")
 
-  wl_add_flag(WL_GENERIC_CXX_FLAGS "-std=c++11")
+  wl_add_flag(WL_GENERIC_CXX_FLAGS "-std=gnu++11")
 endif()
 
 # Cross-compile-unit optimization slows linking significantly.