https://bugs.gentoo.org/904534
--- a/ogr/ogrsf_frmts/flatgeobuf/CMakeLists.txt
+++ b/ogr/ogrsf_frmts/flatgeobuf/CMakeLists.txt
@@ -8,6 +8,7 @@
           ogrflatgeobufeditablelayer.cpp
           PLUGIN_CAPABLE
           NO_DEPS)
+set_property(TARGET ogr_FlatGeobuf PROPERTY CXX_STANDARD 17)
 gdal_standard_includes(ogr_FlatGeobuf)
 target_include_directories(ogr_FlatGeobuf PRIVATE $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>
                                                   $<TARGET_PROPERTY:ogrsf_generic,SOURCE_DIR>)