diff --git a/CMakeLists.txt b/CMakeLists.txt
index 107e8349d..be97e3451 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -747,8 +747,11 @@ if(BUILD_OPENEMU)
 endif()
 
 if(BUILD_SDL)
-	add_definitions(-DBUILD_SDL)
 	add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/src/platform/sdl ${CMAKE_CURRENT_BINARY_DIR}/sdl)
+	# The SDL platform CMakeLists could decide to disable SDL, so check again before adding the define.
+	if(BUILD_SDL)
+		add_definitions(-DBUILD_SDL)
+	endif()
 endif()
 
 if(BUILD_QT)
diff --git a/src/platform/sdl/CMakeLists.txt b/src/platform/sdl/CMakeLists.txt
index 14a377f57..f4b4c37b9 100644
--- a/src/platform/sdl/CMakeLists.txt
+++ b/src/platform/sdl/CMakeLists.txt
@@ -24,6 +24,8 @@ if (NOT SDL2_FOUND AND NOT SDL_FOUND)
 	return()
 endif()
 
+add_definitions(-DBUILD_SDL)
+
 find_feature(USE_PIXMAN "pixman-1")
 if(USE_PIXMAN)
 	add_definitions(-DUSE_PIXMAN)