diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5912af1..5c2a9f4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -58,7 +58,7 @@ add_compile_definitions(
 if(CMAKE_Fortran_COMPILER_ID MATCHES "GNU")
   set(CMAKE_Fortran_FLAGS "${CMAKE_Fortran_FLAGS} -fbacktrace -fconvert=big-endian -ffree-line-length-none -ffixed-line-length-none")
   if(${CMAKE_Fortran_COMPILER_VERSION} VERSION_GREATER_EQUAL 10)
-    list(APPEND CMAKE_Fortran_FLAGS "-fallow-argument-mismatch")
+    set(CMAKE_Fortran_FLAGS "${CMAKE_Fortran_FLAGS} -fallow-argument-mismatch")
   endif()
   set(CMAKE_Fortran_FLAGS_RELEASE "-O")
   set(CMAKE_Fortran_FLAGS_DEBUG "-g -Wall -Og -ffpe-trap=zero,overflow -fcheck=bounds")