diff --git a/bench/CMakeLists.txt b/bench/CMakeLists.txt
index 109a6b0..aba6dc9 100644
--- a/bench/CMakeLists.txt
+++ b/bench/CMakeLists.txt
@@ -41,8 +41,8 @@ PREPEND(barnes_sources barnes/ ${barnes_sources})
 message(STATUS "${CMAKE_C_COMPILER_ID}")
 if(CMAKE_C_COMPILER_ID MATCHES "AppleClang|Clang|GNU")
   set(FLAGS " -w -Wno-implicit-function-declaration -Wno-implicit-int -Wno-int-conversion")
-  list(APPEND CMAKE_C_FLAGS ${FLAGS})
-  list(APPEND CMAKE_CXX_FLAGS ${FLAGS})
+  string(APPEND CMAKE_C_FLAGS ${FLAGS})
+  string(APPEND CMAKE_CXX_FLAGS ${FLAGS})
 endif()
 
 add_executable(cfrac ${cfrac_sources})