diff --git a/src/bitcoinrpc.h b/src/bitcoinrpc.h
index 275369ddd201c..0c1c722b50f06 100644
--- a/src/bitcoinrpc.h
+++ b/src/bitcoinrpc.h
@@ -49,10 +49,13 @@ enum RPCErrorCode
     RPC_INVALID_PARAMETER           = -8,  // Invalid, missing or duplicate parameter
     RPC_DATABASE_ERROR              = -20, // Database error
     RPC_DESERIALIZATION_ERROR       = -22, // Error parsing or validating structure in raw format
+    RPC_SERVER_NOT_STARTED          = -18, // RPC server was not started (StartRPCThreads() not called)
 
     // P2P client errors
     RPC_CLIENT_NOT_CONNECTED        = -9,  // Bitcoin is not connected
     RPC_CLIENT_IN_INITIAL_DOWNLOAD  = -10, // Still downloading initial blocks
+    RPC_CLIENT_NODE_ALREADY_ADDED   = -23, // Node is already added
+    RPC_CLIENT_NODE_NOT_ADDED       = -24, // Node has not been added before
 
     // Wallet errors
     RPC_WALLET_ERROR                = -4,  // Unspecified problem with wallet (key not found etc.)
diff --git a/src/rpcnet.cpp b/src/rpcnet.cpp
index 3c92739852633..5d87a2449fc9d 100644
--- a/src/rpcnet.cpp
+++ b/src/rpcnet.cpp
@@ -27,7 +27,7 @@ Value ping(const Array& params, bool fHelp)
             "Requests that a ping be sent to all other nodes, to measure ping time.\n"
             "Results provided in getpeerinfo, pingtime and pingwait fields are decimal seconds.\n"
             "Ping command is handled in queue with all other commands, so it measures processing backlog, not just network ping.");
-    
+
     // Request that each node send a ping during next message processing pass
     LOCK(cs_vNodes);
     BOOST_FOREACH(CNode* pNode, vNodes) {
@@ -120,13 +120,13 @@ Value addnode(const Array& params, bool fHelp)
     if (strCommand == "add")
     {
         if (it != vAddedNodes.end())
-            throw JSONRPCError(-23, "Error: Node already added");
+            throw JSONRPCError(RPC_CLIENT_NODE_ALREADY_ADDED, "Error: Node already added");
         vAddedNodes.push_back(strNode);
     }
     else if(strCommand == "remove")
     {
         if (it == vAddedNodes.end())
-            throw JSONRPCError(-24, "Error: Node has not been added.");
+            throw JSONRPCError(RPC_CLIENT_NODE_NOT_ADDED, "Error: Node has not been added.");
         vAddedNodes.erase(it);
     }
 
@@ -163,7 +163,7 @@ Value getaddednodeinfo(const Array& params, bool fHelp)
                 break;
             }
         if (laddedNodes.size() == 0)
-            throw JSONRPCError(-24, "Error: Node has not been added.");
+            throw JSONRPCError(RPC_CLIENT_NODE_NOT_ADDED, "Error: Node has not been added.");
     }
 
     if (!fDns)
diff --git a/src/rpcwallet.cpp b/src/rpcwallet.cpp
index 7aae9ddb733df..fe22dfe54c5a6 100644
--- a/src/rpcwallet.cpp
+++ b/src/rpcwallet.cpp
@@ -1271,7 +1271,7 @@ Value keypoolrefill(const Array& params, bool fHelp)
     unsigned int kpSize = max(GetArg("-keypool", 100), 0LL);
     if (params.size() > 0) {
         if (params[0].get_int() < 0)
-            throw JSONRPCError(-8, "Invalid parameter, expected valid size");
+            throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, expected valid size");
         kpSize = (unsigned int) params[0].get_int();
     }
 
@@ -1301,6 +1301,8 @@ Value walletpassphrase(const Array& params, bool fHelp)
             "Stores the wallet decryption key in memory for <timeout> seconds.");
     if (fHelp)
         return true;
+    if (!fServer)
+        throw JSONRPCError(RPC_SERVER_NOT_STARTED, "Error: RPC server was not started, use server=1 to change this.");
     if (!pwalletMain->IsCrypted())
         throw JSONRPCError(RPC_WALLET_WRONG_ENC_STATE, "Error: running with an unencrypted wallet, but walletpassphrase was called.");