diff --git a/git-mergetool--lib.sh b/git-mergetool--lib.sh
index 2defef28cd931f..7225abd81122e6 100644
--- a/git-mergetool--lib.sh
+++ b/git-mergetool--lib.sh
@@ -138,6 +138,10 @@ setup_user_tool () {
 	merge_cmd () {
 		( eval $merge_tool_cmd )
 	}
+
+	list_tool_variants () {
+		echo "$tool"
+	}
 }
 
 setup_tool () {