diff --git a/CMakeLists.txt b/CMakeLists.txt
index fd9f66b..a0064c9 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -42,7 +42,7 @@ if(CMAKE_GENERATOR STREQUAL "Ninja" AND
 	(CMAKE_CXX_COMPILER_ID STREQUAL "Clang" AND NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 3.5)))
 	# Force colored warnings in Ninja’s output if the compiler has -fdiagnostics-color support.
 	# Rationale in https://github.com/ninja-build/ninja/issues/814
-	set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fdiagnostics-color=always")
+	set(CMAKE_CXX_FLAGS "-fdiagnostics-color=always ${CMAKE_CXX_FLAGS}")
 endif()
 
 add_subdirectory(lib/clingo)