diff -r 128efb9d148b -r 02f142b399b1 src/main.h
--- a/src/main.h	Tue Jul 20 01:22:01 2021 +0300
+++ b/src/main.h	Sat Jul 24 01:50:38 2021 +0300
@@ -92,6 +92,12 @@
 	}
 
 	template<typename T>
+	inline bool operator!=(Id<T> one, decltype(NULL_ID))
+	{
+		return one.value != 0;
+	}
+
+	template<typename T>
 	inline bool operator<(Id<T> one, decltype(NULL_ID))
 	{
 		return one.value < 0;