diff --git a/CMakeLists.txt b/CMakeLists.txt
index 919f8134..718b96c5 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -4,7 +4,7 @@ set(PROJECT_LANGUAGES C)
 
 if(DEFINED CMAKE_CXX_COMPILER)
   set(CMAKE_CXX_STANDARD 17)
-  set(PROJECT_LANGUAGES C CXX)
+  list(APPEND PROJECT_LANGUAGES CXX)
 endif(DEFINED CMAKE_CXX_COMPILER)
 
 project(LibVNCServer VERSION 0.9.14 LANGUAGES ${PROJECT_LANGUAGES})