diff --git a/client/web/divkit/src/expressions/funcs/customFuncs.ts b/client/web/divkit/src/expressions/funcs/customFuncs.ts
index ba2ff24ee..ebbc2f718 100644
--- a/client/web/divkit/src/expressions/funcs/customFuncs.ts
+++ b/client/web/divkit/src/expressions/funcs/customFuncs.ts
@@ -108,7 +108,7 @@ export function mergeCustomFunctions(
         return map1 || undefined;
     }
     if (!map1) {
-        return;
+        return map0 || undefined;
     }
 
     const merged = new Map();