diff --git a/cpuminer.go b/cpuminer.go
index a45e70ee..1e473349 100644
--- a/cpuminer.go
+++ b/cpuminer.go
@@ -548,14 +548,6 @@ func (m *CPUMiner) NumWorkers() int32 {
 func (m *CPUMiner) GenerateNBlocks(n uint32) ([]*chainhash.Hash, error) {
 	m.Lock()
 
-	// Respond with an error if there's virtually 0 chance of CPU-mining a block.
-	if !m.cfg.ChainParams.GenerateSupported {
-		m.Unlock()
-		return nil, errors.New("No support for `generate` on the current " +
-			"network, " + m.cfg.ChainParams.Net.String() +
-			", as it's unlikely to be possible to CPU-mine a block.")
-	}
-
 	// Respond with an error if server is already mining.
 	if m.started || m.discreteMining {
 		m.Unlock()
diff --git a/rpcserver.go b/rpcserver.go
index 74f8b8e4..5c5547aa 100644
--- a/rpcserver.go
+++ b/rpcserver.go
@@ -856,6 +856,19 @@ func handleGenerate(s *rpcServer, cmd interface{}, closeChan <-chan struct{}) (i
 		}
 	}
 
+	// Respond with an error if there's virtually 0 chance of mining a block
+	// with the CPU.
+	params := s.server.chainParams
+	if !s.server.chainParams.GenerateSupported {
+		return nil, &btcjson.RPCError{
+			Code: btcjson.ErrRPCDifficulty,
+			Message: fmt.Sprintf("No support for `generate` on "+
+				"the current network, %s, as it's unlikely to "+
+				"be possible to main a block with the CPU.",
+				params.Net),
+		}
+	}
+
 	c := cmd.(*btcjson.GenerateCmd)
 
 	// Respond with an error if the client is requesting 0 blocks to be generated.