diff --git a/src/cmake/GeosxOptions.cmake b/src/cmake/GeosxOptions.cmake
index fe3adabcc4b..ebc45c3e929 100644
--- a/src/cmake/GeosxOptions.cmake
+++ b/src/cmake/GeosxOptions.cmake
@@ -147,7 +147,7 @@ message( "CMAKE_CXX_COMPILER_ID = ${CMAKE_CXX_COMPILER_ID}" )
 blt_append_custom_compiler_flag( FLAGS_VAR CMAKE_CXX_FLAGS DEFAULT "${OpenMP_CXX_FLAGS}" )
 blt_append_custom_compiler_flag( FLAGS_VAR CMAKE_CXX_FLAGS
                                  GNU   "-Wpedantic -pedantic-errors -Wshadow -Wfloat-equal -Wcast-align -Wcast-qual"
-                                 CLANG "-Wpedantic -pedantic-errors -Wshadow -Wfloat-equal -Wno-cast-align -Wcast-qual"
+                                 CLANG "-Wpedantic -pedantic-errors -Wshadow -Wfloat-equal -Wno-cast-align -Wcast-qual -Wno-shorten-64-to-32"
                                )
 
 blt_append_custom_compiler_flag( FLAGS_VAR CMAKE_CXX_FLAGS_DEBUG