diff --git a/golded3/gckeys.cpp b/golded3/gckeys.cpp
index ae812b5..709dc9f 100644
--- a/golded3/gckeys.cpp
+++ b/golded3/gckeys.cpp
@@ -989,7 +989,7 @@ static void SetKeybDefaults() {
 //  ------------------------------------------------------------------
 
 //bool CmdKeyCmp(CmdKey a, CmdKey b) {
-bool operator<(CmdKey &a, CmdKey &b) {
+bool operator<(const CmdKey &a, const CmdKey &b) {
 
   int cmp = CmpV(a.type, b.type);
   if(cmp != 0)