1 files changed, 1 insertions, 1 deletions
diff --git a/common/list.h b/common/list.h
index d15913d..cf429e5 100644
--- a/common/list.h
+++ b/common/list.h
@@ -25,7 +25,7 @@ class List : public B {
 		}
 		
 		//! Check whether list is empty or not.
-		operator bool() {
+		operator bool() const {
 			return !B::empty();
 		}