diff --git a/CMakeLists.txt b/CMakeLists.txt
index c76e7e6e3..d172ac250 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -283,6 +283,8 @@ set(PLATFORM_LIBS)
 
 # Allegro 4 backend
 if(USE_ALLEG4_BACKEND)
+  add_definitions(-DUSE_ALLEG4_BACKEND)
+
   if(USE_SHARED_ALLEGRO4)
     # Find the shared Allegro 4 library
     find_library(LIBALLEGRO4_LIBRARY alleg)
@@ -313,6 +315,11 @@ if(USE_ALLEG4_BACKEND)
   endif()
 endif()
 
+# Skia backend
+if(USE_SKIA_BACKEND)
+  add_definitions(-DUSE_SKIA_BACKEND)
+endif()
+
 # -- Unix --
 
 if(UNIX AND NOT APPLE AND NOT BEOS)