diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -2534,8 +2534,8 @@
              "progress report (in %) of the current scan"},
             {"scanobjects",
              RPCArg::Type::ARR,
-             RPCArg::Optional::NO,
-             "Array of scan objects\n"
+             RPCArg::Optional::OMITTED,
+             "Array of scan objects. Required for \"start\" action\n"
              "                                  Every scan object is either a "
              "string descriptor or an object:",
              {
@@ -2628,6 +2628,13 @@
                 RPC_INVALID_PARAMETER,
                 "Scan already in progress, use action \"abort\" or \"status\"");
         }
+
+        if (request.params.size() < 2) {
+            throw JSONRPCError(
+                RPC_MISC_ERROR,
+                "scanobjects argument is required for the start action");
+        }
+
         std::set<CScript> needles;
         std::map<CScript, std::string> descriptors;
         Amount total_in = Amount::zero();
diff --git a/test/functional/rpc_scantxoutset.py b/test/functional/rpc_scantxoutset.py
--- a/test/functional/rpc_scantxoutset.py
+++ b/test/functional/rpc_scantxoutset.py
@@ -216,6 +216,16 @@
                       'pkh([0c5f9a1e/1/1/1500]03832901c250025da2aebae2bfb38d5c703a57ab66ad477f9c578bfbcd78abca6f)#vchwd07g',
                       'pkh([0c5f9a1e/1/1/1]030d820fc9e8211c4169be8530efbc632775d8286167afd178caaf1089b77daba7)#z2t3ypsa'])
 
+        # Check that status and abort don't need second arg
+        assert_equal(self.nodes[0].scantxoutset("status"), None)
+        assert_equal(self.nodes[0].scantxoutset("abort"), False)
+
+        # Check that second arg is needed for start
+        assert_raises_rpc_error(-1,
+                                "scanobjects argument is required for the start action",
+                                self.nodes[0].scantxoutset,
+                                "start")
+
 
 if __name__ == '__main__':
     ScantxoutsetTest().main()