diff --git a/CMakeLists.txt b/CMakeLists.txt
index c260e84..66f0c4a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -30,12 +30,12 @@ cmake_dependent_option(SAVETOOL_USE_SYSTEM_LIBZIP "Use a system-wide version of
 cmake_dependent_option(SAVETOOL_USE_SYSTEM_EFSW "Use a system-wide version of EFSW." ON "SAVETOOL_USE_SYSTEM_LIBS" OFF)
 cmake_dependent_option(SAVETOOL_USE_SYSTEM_LIBCURL "Use a system-wide version of libcurl." ON "SAVETOOL_USE_SYSTEM_LIBS" OFF)
 
-if(NOT SAVETOOL_USE_SYSTEM_LIBS)
+if(NOT SAVETOOL_USE_SYSTEM_LIBS OR NOT (SAVETOOL_USE_SYSTEM_CORRADE_MAGNUM AND SAVETOOL_USE_SYSTEM_SDL2 AND SAVETOOL_USE_SYSTEM_LIBZIP AND SAVETOOL_USE_SYSTEM_EFSW AND SAVETOOL_USE_SYSTEM_LIBCURL))
     # Generic variables shared by multiple libs that don't provide their own.
     set(BUILD_SHARED_LIBS OFF CACHE BOOL "" FORCE)
     set(BUILD_STATIC_LIBS ON CACHE BOOL "" FORCE)
     set(BUILD_TESTING OFF CACHE BOOL "" FORCE)
-endif(NOT SAVETOOL_USE_SYSTEM_LIBS)
+endif()
 
 if(NOT SAVETOOL_USE_SYSTEM_SDL2)
     set(DIRECTX OFF CACHE BOOL "" FORCE) # We use OpenGL.