diff --git a/src/facade/op_status.cc b/src/facade/op_status.cc
index 6441a2ba7..d89285870 100644
--- a/src/facade/op_status.cc
+++ b/src/facade/op_status.cc
@@ -28,6 +28,8 @@ std::string_view StatusToMsg(OpStatus status) {
       return "-BUSYGROUP Consumer Group name already exists";
     case OpStatus::INVALID_NUMERIC_RESULT:
       return kInvalidNumericResult;
+    case OpStatus::AT_LEAST_ONE_KEY:
+      return "at least 1 input key is needed for this command";
     default:
       LOG(ERROR) << "Unsupported status " << status;
       return "Internal error";
diff --git a/src/facade/op_status.h b/src/facade/op_status.h
index 0f175afc2..f96fdba7c 100644
--- a/src/facade/op_status.h
+++ b/src/facade/op_status.h
@@ -27,6 +27,7 @@ enum class OpStatus : uint16_t {
   ENTRIES_ADDED_SMALL,
   INVALID_NUMERIC_RESULT,
   CANCELLED,
+  AT_LEAST_ONE_KEY,
 };
 
 class OpResultBase {
diff --git a/src/server/transaction.cc b/src/server/transaction.cc
index b3b4972a0..795de10ba 100644
--- a/src/server/transaction.cc
+++ b/src/server/transaction.cc
@@ -1462,12 +1462,10 @@ OpResult<KeyIndex> DetermineKeys(const CommandId* cid, CmdArgList args) {
     if (!absl::SimpleAtoi(num, &num_custom_keys) || num_custom_keys < 0)
       return OpStatus::INVALID_INT;
 
-    if (name == "ZDIFF" && num_custom_keys == 0) {
-      return OpStatus::INVALID_INT;
-    }
-
-    if (name == "ZUNION" && num_custom_keys == 0) {
-      return OpStatus::SYNTAX_ERR;
+    if (num_custom_keys == 0 &&
+        (absl::StartsWith(name, "ZDIFF") || absl::StartsWith(name, "ZUNION") ||
+         absl::StartsWith(name, "ZINTER"))) {
+      return OpStatus::AT_LEAST_ONE_KEY;
     }
 
     if (args.size() < size_t(num_custom_keys) + num_keys_index + 1)
diff --git a/src/server/zset_family_test.cc b/src/server/zset_family_test.cc
index a5c442ab4..f0f5a22e2 100644
--- a/src/server/zset_family_test.cc
+++ b/src/server/zset_family_test.cc
@@ -322,7 +322,7 @@ TEST_F(ZSetFamilyTest, ZUnionError) {
   EXPECT_THAT(resp, ErrArg("wrong number of arguments"));
 
   resp = Run({"zunion", "0", "myset"});
-  EXPECT_THAT(resp, ErrArg("syntax error"));
+  EXPECT_THAT(resp, ErrArg("at least 1 input key is needed"));
 
   resp = Run({"zunion", "3", "z1", "z2", "z3", "weights", "1", "1", "k"});
   EXPECT_THAT(resp, ErrArg("weight value is not a float"));
@@ -402,7 +402,7 @@ TEST_F(ZSetFamilyTest, ZUnionStore) {
   EXPECT_THAT(resp, ErrArg("wrong number of arguments"));
 
   resp = Run({"zunionstore", "key", "0", "aggregate"});
-  EXPECT_THAT(resp, ErrArg("syntax error"));
+  EXPECT_THAT(resp, ErrArg("at least 1 input key is needed"));
 
   resp = Run({"zunionstore", "key", "0", "aggregate", "sum"});
   EXPECT_THAT(resp, ErrArg("at least 1 input key is needed"));
@@ -476,11 +476,12 @@ TEST_F(ZSetFamilyTest, ZInterStore) {
 TEST_F(ZSetFamilyTest, ZInterCard) {
   EXPECT_EQ(3, CheckedInt({"zadd", "z1", "1", "a", "2", "b", "3", "c"}));
   EXPECT_EQ(3, CheckedInt({"zadd", "z2", "2", "b", "3", "c", "4", "d"}));
-  RespExpr resp;
 
   EXPECT_EQ(2, CheckedInt({"zintercard", "2", "z1", "z2"}));
   EXPECT_EQ(1, CheckedInt({"zintercard", "2", "z1", "z2", "LIMIT", "1"}));
 
+  RespExpr resp;
+
   resp = Run({"zintercard", "2", "z1", "z2", "LIM"});
   EXPECT_THAT(resp, ErrArg("syntax error"));
   resp = Run({"zintercard", "2", "z1", "z2", "LIMIT"});
@@ -488,6 +489,9 @@ TEST_F(ZSetFamilyTest, ZInterCard) {
   resp = Run({"zintercard", "2", "z1", "z2", "LIMIT", "a"});
   EXPECT_THAT(resp, ErrArg("limit value is not a positive integer"));
 
+  resp = Run({"zintercard", "0", "z1"});
+  EXPECT_THAT(resp, ErrArg("at least 1 input"));
+
   // support for sets
   EXPECT_EQ(3, CheckedInt({"sadd", "s2", "b", "c", "d"}));
   EXPECT_EQ(2, CheckedInt({"zintercard", "2", "z1", "s2"}));
@@ -632,10 +636,10 @@ TEST_F(ZSetFamilyTest, ZDiffError) {
   EXPECT_THAT(resp, ErrArg("wrong number of arguments"));
 
   resp = Run({"zdiff", "0", "z1"});
-  EXPECT_THAT(resp, ErrArg("value is not an integer or out of range"));
+  EXPECT_THAT(resp, ErrArg("at least 1 input key is needed"));
 
   resp = Run({"zdiff", "0", "z1", "z2"});
-  EXPECT_THAT(resp, ErrArg("value is not an integer or out of range"));
+  EXPECT_THAT(resp, ErrArg("at least 1 input key is needed"));
 }
 
 TEST_F(ZSetFamilyTest, ZDiff) {