diff --git a/velox/functions/sparksql/Register.cpp b/velox/functions/sparksql/Register.cpp
index efc8758343a65..b918bc61dff34 100644
--- a/velox/functions/sparksql/Register.cpp
+++ b/velox/functions/sparksql/Register.cpp
@@ -189,7 +189,10 @@ void registerFunctions(const std::string& prefix) {
   registerFunction<SubstringIndexFunction, Varchar, Varchar, Varchar, int32_t>(
       {prefix + "substring_index"});
   exec::registerStatefulVectorFunction(
-      prefix + "concat_ws", concatWsSignatures(), makeConcatWs);
+      prefix + "concat_ws",
+      concatWsSignatures(),
+      makeConcatWs,
+      exec::VectorFunctionMetadataBuilder().defaultNullBehavior(false).build());
 
   registerFunction<Md5Function, Varchar, Varbinary>({prefix + "md5"});
   registerFunction<Sha1HexStringFunction, Varchar, Varbinary>(
diff --git a/velox/functions/sparksql/String.cpp b/velox/functions/sparksql/String.cpp
index 567fc6721f56a..6de344453fa8d 100644
--- a/velox/functions/sparksql/String.cpp
+++ b/velox/functions/sparksql/String.cpp
@@ -290,10 +290,6 @@ class ConcatWs : public exec::VectorFunction {
  public:
   explicit ConcatWs(const std::string& separator) : separator_(separator) {}
 
-  bool isDefaultNullBehavior() const override {
-    return false;
-  }
-
   void apply(
       const SelectivityVector& selected,
       std::vector<VectorPtr>& args,