--- GDCM-3.0.24/CMakeLists.txt
+++ GDCM-3.0.24/CMakeLists.txt
@@ -335,6 +335,7 @@ mark_as_advanced(
 option(GDCM_USE_SYSTEM_POPPLER "Use system poppler (pdf)" OFF)
 if(GDCM_USE_SYSTEM_POPPLER)
   find_package(Poppler REQUIRED)
+  set(CMAKE_CXX_STANDARD 20)
 endif()
 mark_as_advanced(GDCM_USE_SYSTEM_POPPLER)