1 files changed, 1 insertions, 1 deletions
diff --git a/klm/lm/state.hh b/klm/lm/state.hh
index d8e6c132..a6b9accb 100644
--- a/klm/lm/state.hh
+++ b/klm/lm/state.hh
@@ -91,7 +91,7 @@ inline uint64_t hash_value(const Left &left) {
 }
 
 struct ChartState {
-  bool operator==(const ChartState &other) {
+  bool operator==(const ChartState &other) const {
     return (right == other.right) && (left == other.left);
   }