diff --git a/platforms/linux/riscv64-clang.toolchain.cmake b/platforms/linux/riscv64-clang.toolchain.cmake
index cec5f7d734..612be05eab 100644
--- a/platforms/linux/riscv64-clang.toolchain.cmake
+++ b/platforms/linux/riscv64-clang.toolchain.cmake
@@ -18,7 +18,7 @@ set(CMAKE_ASM_COMPILER_TARGET ${CLANG_TARGET_TRIPLE})
 set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
 
 set(CMAKE_C_FLAGS "-march=rv64gc --gcc-toolchain=${RISCV_GCC_INSTALL_ROOT} -w ${CMAKE_C_FLAGS}")
-set(CMAKE_CXX_FLAGS "-march=rv64gc --gcc-toolchain=${RISCV_GCC_INSTALL_ROOT} -w ${CXX_FLAGS}")
+set(CMAKE_CXX_FLAGS "-march=rv64gc --gcc-toolchain=${RISCV_GCC_INSTALL_ROOT} -w ${CMAKE_CXX_FLAGS}")
 
 set(CMAKE_FIND_ROOT_PATH ${CMAKE_SYSROOT})
 set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)