diff --git a/cpp/cmake_modules/UseCython.cmake b/cpp/cmake_modules/UseCython.cmake
index 0d4b17d3e5724..0b65a7842f97f 100644
--- a/cpp/cmake_modules/UseCython.cmake
+++ b/cpp/cmake_modules/UseCython.cmake
@@ -107,8 +107,9 @@ function(compile_pyx
   endif()
 
   if(NOT WIN32)
-    if("${CMAKE_BUILD_TYPE}" STREQUAL "Debug"
-       OR "${CMAKE_BUILD_TYPE}" STREQUAL "RelWithDebInfo")
+    string( TOLOWER "${CMAKE_BUILD_TYPE}" build_type )
+    if("${build_type}" STREQUAL "debug"
+       OR "${build_type}" STREQUAL "relwithdebinfo")
       set(cython_debug_arg "--gdb")
     endif()
   endif()