diff --git a/backends/CMakeLists.txt b/backends/CMakeLists.txt
index d005be0b6d11b5286e7e4342d212698ce5befed8..9982d868ffcfafaf9e0a5127ea0629620fa78680 100644
--- a/backends/CMakeLists.txt
+++ b/backends/CMakeLists.txt
@@ -1,5 +1,7 @@
 if (PROTOBUF_FOUND)
-	ADD_SUBDIRECTORY(libpurple)
+	if ( PURPLE_LIBRARY AND PURPLE_INCLUDE_DIR )
+		ADD_SUBDIRECTORY(libpurple)
+	endif()
 
 	if (IRC_FOUND)
 		ADD_SUBDIRECTORY(libircclient-qt)