diff --git a/CMakeLists.txt b/CMakeLists.txt
index eef1cb7fde..6c715010f9 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -831,6 +831,12 @@ else()
   list( APPEND PROJECT_COMPILE_DEFINITIONS_CONFCHECK FSEEK_OK )
 endif()
 
+if ( ${NOUNDERSCORE_SYMBOL} )
+  list( APPEND PROJECT_COMPILE_DEFINITIONS_CONFCHECK NOUNDERSCORE )
+elseif( ${UNDERSCORE_SYMBOL} )
+  list( APPEND PROJECT_COMPILE_DEFINITIONS_CONFCHECK UNDERSCORE )
+endif()
+
 # I don't believe these are used anymore...
 # $<$<BOOL:${MPI2_SUPPORT}>:MPI2_SUPPORT=$<BOOL:${MPI2_SUPPORT}>>
 # $<$<BOOL:${MPI2_THREAD_SUPPORT}>:MPI2_THREAD_SUPPORT=$<BOOL:${MPI2_THREAD_SUPPORT}>>