diff --git a/libs/main/core/piconstchars.h b/libs/main/core/piconstchars.h
index 5aff7412..af99701a 100644
--- a/libs/main/core/piconstchars.h
+++ b/libs/main/core/piconstchars.h
@@ -130,8 +130,9 @@ public:
 	//! \~english Compare operator.
 	//! \~russian Оператор сравнения.
 	inline bool operator <(const PIConstChars & s) const {
-		if (isNull() && s.isNull()) return false;
-		if (isNull() xor s.isNull()) return false;
+		if ( isNull() &&  s.isNull()) return false;
+		if ( isNull() && !s.isNull()) return true ;
+		if (!isNull() &&  s.isNull()) return false;
 		if (size() == s.size())
 			return strcmp(str, s.str) < 0;
 		return size() < s.size();
@@ -140,8 +141,9 @@ public:
 	//! \~english Compare operator.
 	//! \~russian Оператор сравнения.
 	inline bool operator >(const PIConstChars & s) const {
-		if (isNull() && s.isNull()) return false;
-		if (isNull() xor s.isNull()) return false;
+		if ( isNull() &&  s.isNull()) return false;
+		if ( isNull() && !s.isNull()) return false;
+		if (!isNull() &&  s.isNull()) return true ;
 		if (size() == s.size())
 			return strcmp(str, s.str) > 0;
 		return size() > s.size();
diff --git a/main.cpp b/main.cpp
index 6b1e75c0..690214fd 100644
--- a/main.cpp
+++ b/main.cpp
@@ -39,6 +39,8 @@ int main(int argc, char * argv[]) {
 	cmp(PIConstChars("1c"), PIConstChars("1b"));*/
 
 	PIMap<PIConstChars, int> map;
+	map[PIConstChars()] = 0;
+	map[PIConstChars()] = -1;
 	map["_2"] = 22;
 	map["1"] = 11;
 	map["__3"] = 33;