diff --git a/src/misc/TextHandler.h b/src/misc/TextHandler.h
index b2fc8f6..66772eb 100644
--- a/src/misc/TextHandler.h
+++ b/src/misc/TextHandler.h
@@ -14,7 +14,7 @@ using namespace std;
 
 struct stringLessThan
 {
-	bool operator()(const char *s1, const char *s2)
+	bool operator()(const char *s1, const char *s2) const
 	{
 		return strcmp(s1, s2) < 0;
 	}