diff --git a/binapi/graph/graph_rpc.ba.go b/binapi/graph/graph_rpc.ba.go
index 96a22021..57194ef3 100644
--- a/binapi/graph/graph_rpc.ba.go
+++ b/binapi/graph/graph_rpc.ba.go
@@ -36,7 +36,7 @@ func (c *serviceClient) GraphNodeGet(ctx context.Context, in *GraphNodeGet) (RPC
 }
 
 type RPCService_GraphNodeGetClient interface {
-	Recv() (*GraphNodeDetails, error)
+	Recv() (*GraphNodeDetails, *GraphNodeGetReply, error)
 	api.Stream
 }
 
@@ -44,21 +44,24 @@ type serviceClient_GraphNodeGetClient struct {
 	api.Stream
 }
 
-func (c *serviceClient_GraphNodeGetClient) Recv() (*GraphNodeDetails, error) {
+func (c *serviceClient_GraphNodeGetClient) Recv() (*GraphNodeDetails, *GraphNodeGetReply, error) {
 	msg, err := c.Stream.RecvMsg()
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 	switch m := msg.(type) {
 	case *GraphNodeDetails:
-		return m, nil
+		return m, nil, nil
 	case *GraphNodeGetReply:
+		if err := api.RetvalToVPPApiError(m.Retval); err != nil {
+			return nil, nil, err
+		}
 		err = c.Stream.Close()
 		if err != nil {
-			return nil, err
+			return nil, nil, err
 		}
-		return nil, io.EOF
+		return nil, m, io.EOF
 	default:
-		return nil, fmt.Errorf("unexpected message: %T %v", m, m)
+		return nil, nil, fmt.Errorf("unexpected message: %T %v", m, m)
 	}
 }
diff --git a/binapi/interface/interface_rpc.ba.go b/binapi/interface/interface_rpc.ba.go
index a1754032..8103d7cb 100644
--- a/binapi/interface/interface_rpc.ba.go
+++ b/binapi/interface/interface_rpc.ba.go
@@ -406,7 +406,7 @@ func (c *serviceClient) SwInterfaceTxPlacementGet(ctx context.Context, in *SwInt
 }
 
 type RPCService_SwInterfaceTxPlacementGetClient interface {
-	Recv() (*SwInterfaceTxPlacementDetails, error)
+	Recv() (*SwInterfaceTxPlacementDetails, *SwInterfaceTxPlacementGetReply, error)
 	api.Stream
 }
 
@@ -414,22 +414,25 @@ type serviceClient_SwInterfaceTxPlacementGetClient struct {
 	api.Stream
 }
 
-func (c *serviceClient_SwInterfaceTxPlacementGetClient) Recv() (*SwInterfaceTxPlacementDetails, error) {
+func (c *serviceClient_SwInterfaceTxPlacementGetClient) Recv() (*SwInterfaceTxPlacementDetails, *SwInterfaceTxPlacementGetReply, error) {
 	msg, err := c.Stream.RecvMsg()
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 	switch m := msg.(type) {
 	case *SwInterfaceTxPlacementDetails:
-		return m, nil
+		return m, nil, nil
 	case *SwInterfaceTxPlacementGetReply:
+		if err := api.RetvalToVPPApiError(m.Retval); err != nil {
+			return nil, nil, err
+		}
 		err = c.Stream.Close()
 		if err != nil {
-			return nil, err
+			return nil, nil, err
 		}
-		return nil, io.EOF
+		return nil, m, io.EOF
 	default:
-		return nil, fmt.Errorf("unexpected message: %T %v", m, m)
+		return nil, nil, fmt.Errorf("unexpected message: %T %v", m, m)
 	}
 }
 
diff --git a/binapi/ip/ip_rpc.ba.go b/binapi/ip/ip_rpc.ba.go
index 31124fcd..255a3b32 100644
--- a/binapi/ip/ip_rpc.ba.go
+++ b/binapi/ip/ip_rpc.ba.go
@@ -359,7 +359,7 @@ func (c *serviceClient) IPPathMtuGet(ctx context.Context, in *IPPathMtuGet) (RPC
 }
 
 type RPCService_IPPathMtuGetClient interface {
-	Recv() (*IPPathMtuDetails, error)
+	Recv() (*IPPathMtuDetails, *IPPathMtuGetReply, error)
 	api.Stream
 }
 
@@ -367,22 +367,25 @@ type serviceClient_IPPathMtuGetClient struct {
 	api.Stream
 }
 
-func (c *serviceClient_IPPathMtuGetClient) Recv() (*IPPathMtuDetails, error) {
+func (c *serviceClient_IPPathMtuGetClient) Recv() (*IPPathMtuDetails, *IPPathMtuGetReply, error) {
 	msg, err := c.Stream.RecvMsg()
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 	switch m := msg.(type) {
 	case *IPPathMtuDetails:
-		return m, nil
+		return m, nil, nil
 	case *IPPathMtuGetReply:
+		if err := api.RetvalToVPPApiError(m.Retval); err != nil {
+			return nil, nil, err
+		}
 		err = c.Stream.Close()
 		if err != nil {
-			return nil, err
+			return nil, nil, err
 		}
-		return nil, io.EOF
+		return nil, m, io.EOF
 	default:
-		return nil, fmt.Errorf("unexpected message: %T %v", m, m)
+		return nil, nil, fmt.Errorf("unexpected message: %T %v", m, m)
 	}
 }
 
diff --git a/binapi/ipfix_export/ipfix_export_rpc.ba.go b/binapi/ipfix_export/ipfix_export_rpc.ba.go
index f34b4e64..11cecf36 100644
--- a/binapi/ipfix_export/ipfix_export_rpc.ba.go
+++ b/binapi/ipfix_export/ipfix_export_rpc.ba.go
@@ -45,7 +45,7 @@ func (c *serviceClient) IpfixAllExporterGet(ctx context.Context, in *IpfixAllExp
 }
 
 type RPCService_IpfixAllExporterGetClient interface {
-	Recv() (*IpfixAllExporterDetails, error)
+	Recv() (*IpfixAllExporterDetails, *IpfixAllExporterGetReply, error)
 	api.Stream
 }
 
@@ -53,22 +53,25 @@ type serviceClient_IpfixAllExporterGetClient struct {
 	api.Stream
 }
 
-func (c *serviceClient_IpfixAllExporterGetClient) Recv() (*IpfixAllExporterDetails, error) {
+func (c *serviceClient_IpfixAllExporterGetClient) Recv() (*IpfixAllExporterDetails, *IpfixAllExporterGetReply, error) {
 	msg, err := c.Stream.RecvMsg()
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 	switch m := msg.(type) {
 	case *IpfixAllExporterDetails:
-		return m, nil
+		return m, nil, nil
 	case *IpfixAllExporterGetReply:
+		if err := api.RetvalToVPPApiError(m.Retval); err != nil {
+			return nil, nil, err
+		}
 		err = c.Stream.Close()
 		if err != nil {
-			return nil, err
+			return nil, nil, err
 		}
-		return nil, io.EOF
+		return nil, m, io.EOF
 	default:
-		return nil, fmt.Errorf("unexpected message: %T %v", m, m)
+		return nil, nil, fmt.Errorf("unexpected message: %T %v", m, m)
 	}
 }
 
diff --git a/binapi/lcp/lcp_rpc.ba.go b/binapi/lcp/lcp_rpc.ba.go
index 1010d03c..03fa12c7 100644
--- a/binapi/lcp/lcp_rpc.ba.go
+++ b/binapi/lcp/lcp_rpc.ba.go
@@ -78,7 +78,7 @@ func (c *serviceClient) LcpItfPairGet(ctx context.Context, in *LcpItfPairGet) (R
 }
 
 type RPCService_LcpItfPairGetClient interface {
-	Recv() (*LcpItfPairDetails, error)
+	Recv() (*LcpItfPairDetails, *LcpItfPairGetReply, error)
 	api.Stream
 }
 
@@ -86,22 +86,25 @@ type serviceClient_LcpItfPairGetClient struct {
 	api.Stream
 }
 
-func (c *serviceClient_LcpItfPairGetClient) Recv() (*LcpItfPairDetails, error) {
+func (c *serviceClient_LcpItfPairGetClient) Recv() (*LcpItfPairDetails, *LcpItfPairGetReply, error) {
 	msg, err := c.Stream.RecvMsg()
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 	switch m := msg.(type) {
 	case *LcpItfPairDetails:
-		return m, nil
+		return m, nil, nil
 	case *LcpItfPairGetReply:
+		if err := api.RetvalToVPPApiError(m.Retval); err != nil {
+			return nil, nil, err
+		}
 		err = c.Stream.Close()
 		if err != nil {
-			return nil, err
+			return nil, nil, err
 		}
-		return nil, io.EOF
+		return nil, m, io.EOF
 	default:
-		return nil, fmt.Errorf("unexpected message: %T %v", m, m)
+		return nil, nil, fmt.Errorf("unexpected message: %T %v", m, m)
 	}
 }
 
diff --git a/binapi/map/map_rpc.ba.go b/binapi/map/map_rpc.ba.go
index f667d67c..ee5faefa 100644
--- a/binapi/map/map_rpc.ba.go
+++ b/binapi/map/map_rpc.ba.go
@@ -122,7 +122,7 @@ func (c *serviceClient) MapDomainsGet(ctx context.Context, in *MapDomainsGet) (R
 }
 
 type RPCService_MapDomainsGetClient interface {
-	Recv() (*MapDomainDetails, error)
+	Recv() (*MapDomainDetails, *MapDomainsGetReply, error)
 	api.Stream
 }
 
@@ -130,22 +130,25 @@ type serviceClient_MapDomainsGetClient struct {
 	api.Stream
 }
 
-func (c *serviceClient_MapDomainsGetClient) Recv() (*MapDomainDetails, error) {
+func (c *serviceClient_MapDomainsGetClient) Recv() (*MapDomainDetails, *MapDomainsGetReply, error) {
 	msg, err := c.Stream.RecvMsg()
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 	switch m := msg.(type) {
 	case *MapDomainDetails:
-		return m, nil
+		return m, nil, nil
 	case *MapDomainsGetReply:
+		if err := api.RetvalToVPPApiError(m.Retval); err != nil {
+			return nil, nil, err
+		}
 		err = c.Stream.Close()
 		if err != nil {
-			return nil, err
+			return nil, nil, err
 		}
-		return nil, io.EOF
+		return nil, m, io.EOF
 	default:
-		return nil, fmt.Errorf("unexpected message: %T %v", m, m)
+		return nil, nil, fmt.Errorf("unexpected message: %T %v", m, m)
 	}
 }
 
diff --git a/binapi/mss_clamp/mss_clamp_rpc.ba.go b/binapi/mss_clamp/mss_clamp_rpc.ba.go
index d533af9a..704d1c83 100644
--- a/binapi/mss_clamp/mss_clamp_rpc.ba.go
+++ b/binapi/mss_clamp/mss_clamp_rpc.ba.go
@@ -46,7 +46,7 @@ func (c *serviceClient) MssClampGet(ctx context.Context, in *MssClampGet) (RPCSe
 }
 
 type RPCService_MssClampGetClient interface {
-	Recv() (*MssClampDetails, error)
+	Recv() (*MssClampDetails, *MssClampGetReply, error)
 	api.Stream
 }
 
@@ -54,21 +54,24 @@ type serviceClient_MssClampGetClient struct {
 	api.Stream
 }
 
-func (c *serviceClient_MssClampGetClient) Recv() (*MssClampDetails, error) {
+func (c *serviceClient_MssClampGetClient) Recv() (*MssClampDetails, *MssClampGetReply, error) {
 	msg, err := c.Stream.RecvMsg()
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 	switch m := msg.(type) {
 	case *MssClampDetails:
-		return m, nil
+		return m, nil, nil
 	case *MssClampGetReply:
+		if err := api.RetvalToVPPApiError(m.Retval); err != nil {
+			return nil, nil, err
+		}
 		err = c.Stream.Close()
 		if err != nil {
-			return nil, err
+			return nil, nil, err
 		}
-		return nil, io.EOF
+		return nil, m, io.EOF
 	default:
-		return nil, fmt.Errorf("unexpected message: %T %v", m, m)
+		return nil, nil, fmt.Errorf("unexpected message: %T %v", m, m)
 	}
 }
diff --git a/binapi/nat44_ed/nat44_ed_rpc.ba.go b/binapi/nat44_ed/nat44_ed_rpc.ba.go
index 3964bdbf..044cca19 100644
--- a/binapi/nat44_ed/nat44_ed_rpc.ba.go
+++ b/binapi/nat44_ed/nat44_ed_rpc.ba.go
@@ -222,7 +222,7 @@ func (c *serviceClient) Nat44EdOutputInterfaceGet(ctx context.Context, in *Nat44
 }
 
 type RPCService_Nat44EdOutputInterfaceGetClient interface {
-	Recv() (*Nat44EdOutputInterfaceDetails, error)
+	Recv() (*Nat44EdOutputInterfaceDetails, *Nat44EdOutputInterfaceGetReply, error)
 	api.Stream
 }
 
@@ -230,22 +230,25 @@ type serviceClient_Nat44EdOutputInterfaceGetClient struct {
 	api.Stream
 }
 
-func (c *serviceClient_Nat44EdOutputInterfaceGetClient) Recv() (*Nat44EdOutputInterfaceDetails, error) {
+func (c *serviceClient_Nat44EdOutputInterfaceGetClient) Recv() (*Nat44EdOutputInterfaceDetails, *Nat44EdOutputInterfaceGetReply, error) {
 	msg, err := c.Stream.RecvMsg()
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 	switch m := msg.(type) {
 	case *Nat44EdOutputInterfaceDetails:
-		return m, nil
+		return m, nil, nil
 	case *Nat44EdOutputInterfaceGetReply:
+		if err := api.RetvalToVPPApiError(m.Retval); err != nil {
+			return nil, nil, err
+		}
 		err = c.Stream.Close()
 		if err != nil {
-			return nil, err
+			return nil, nil, err
 		}
-		return nil, io.EOF
+		return nil, m, io.EOF
 	default:
-		return nil, fmt.Errorf("unexpected message: %T %v", m, m)
+		return nil, nil, fmt.Errorf("unexpected message: %T %v", m, m)
 	}
 }
 
diff --git a/binapi/nat44_ei/nat44_ei_rpc.ba.go b/binapi/nat44_ei/nat44_ei_rpc.ba.go
index 7656525f..02daae17 100644
--- a/binapi/nat44_ei/nat44_ei_rpc.ba.go
+++ b/binapi/nat44_ei/nat44_ei_rpc.ba.go
@@ -460,7 +460,7 @@ func (c *serviceClient) Nat44EiOutputInterfaceGet(ctx context.Context, in *Nat44
 }
 
 type RPCService_Nat44EiOutputInterfaceGetClient interface {
-	Recv() (*Nat44EiOutputInterfaceDetails, error)
+	Recv() (*Nat44EiOutputInterfaceDetails, *Nat44EiOutputInterfaceGetReply, error)
 	api.Stream
 }
 
@@ -468,22 +468,25 @@ type serviceClient_Nat44EiOutputInterfaceGetClient struct {
 	api.Stream
 }
 
-func (c *serviceClient_Nat44EiOutputInterfaceGetClient) Recv() (*Nat44EiOutputInterfaceDetails, error) {
+func (c *serviceClient_Nat44EiOutputInterfaceGetClient) Recv() (*Nat44EiOutputInterfaceDetails, *Nat44EiOutputInterfaceGetReply, error) {
 	msg, err := c.Stream.RecvMsg()
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 	switch m := msg.(type) {
 	case *Nat44EiOutputInterfaceDetails:
-		return m, nil
+		return m, nil, nil
 	case *Nat44EiOutputInterfaceGetReply:
+		if err := api.RetvalToVPPApiError(m.Retval); err != nil {
+			return nil, nil, err
+		}
 		err = c.Stream.Close()
 		if err != nil {
-			return nil, err
+			return nil, nil, err
 		}
-		return nil, io.EOF
+		return nil, m, io.EOF
 	default:
-		return nil, fmt.Errorf("unexpected message: %T %v", m, m)
+		return nil, nil, fmt.Errorf("unexpected message: %T %v", m, m)
 	}
 }
 
diff --git a/binapi/pnat/pnat_rpc.ba.go b/binapi/pnat/pnat_rpc.ba.go
index a910602c..cb7483a4 100644
--- a/binapi/pnat/pnat_rpc.ba.go
+++ b/binapi/pnat/pnat_rpc.ba.go
@@ -87,7 +87,7 @@ func (c *serviceClient) PnatBindingsGet(ctx context.Context, in *PnatBindingsGet
 }
 
 type RPCService_PnatBindingsGetClient interface {
-	Recv() (*PnatBindingsDetails, error)
+	Recv() (*PnatBindingsDetails, *PnatBindingsGetReply, error)
 	api.Stream
 }
 
@@ -95,22 +95,25 @@ type serviceClient_PnatBindingsGetClient struct {
 	api.Stream
 }
 
-func (c *serviceClient_PnatBindingsGetClient) Recv() (*PnatBindingsDetails, error) {
+func (c *serviceClient_PnatBindingsGetClient) Recv() (*PnatBindingsDetails, *PnatBindingsGetReply, error) {
 	msg, err := c.Stream.RecvMsg()
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 	switch m := msg.(type) {
 	case *PnatBindingsDetails:
-		return m, nil
+		return m, nil, nil
 	case *PnatBindingsGetReply:
+		if err := api.RetvalToVPPApiError(m.Retval); err != nil {
+			return nil, nil, err
+		}
 		err = c.Stream.Close()
 		if err != nil {
-			return nil, err
+			return nil, nil, err
 		}
-		return nil, io.EOF
+		return nil, m, io.EOF
 	default:
-		return nil, fmt.Errorf("unexpected message: %T %v", m, m)
+		return nil, nil, fmt.Errorf("unexpected message: %T %v", m, m)
 	}
 }
 
@@ -127,7 +130,7 @@ func (c *serviceClient) PnatInterfacesGet(ctx context.Context, in *PnatInterface
 }
 
 type RPCService_PnatInterfacesGetClient interface {
-	Recv() (*PnatInterfacesDetails, error)
+	Recv() (*PnatInterfacesDetails, *PnatInterfacesGetReply, error)
 	api.Stream
 }
 
@@ -135,21 +138,24 @@ type serviceClient_PnatInterfacesGetClient struct {
 	api.Stream
 }
 
-func (c *serviceClient_PnatInterfacesGetClient) Recv() (*PnatInterfacesDetails, error) {
+func (c *serviceClient_PnatInterfacesGetClient) Recv() (*PnatInterfacesDetails, *PnatInterfacesGetReply, error) {
 	msg, err := c.Stream.RecvMsg()
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 	switch m := msg.(type) {
 	case *PnatInterfacesDetails:
-		return m, nil
+		return m, nil, nil
 	case *PnatInterfacesGetReply:
+		if err := api.RetvalToVPPApiError(m.Retval); err != nil {
+			return nil, nil, err
+		}
 		err = c.Stream.Close()
 		if err != nil {
-			return nil, err
+			return nil, nil, err
 		}
-		return nil, io.EOF
+		return nil, m, io.EOF
 	default:
-		return nil, fmt.Errorf("unexpected message: %T %v", m, m)
+		return nil, nil, fmt.Errorf("unexpected message: %T %v", m, m)
 	}
 }
diff --git a/binapi/tracedump/tracedump_rpc.ba.go b/binapi/tracedump/tracedump_rpc.ba.go
index a3f9a0ef..1c807d78 100644
--- a/binapi/tracedump/tracedump_rpc.ba.go
+++ b/binapi/tracedump/tracedump_rpc.ba.go
@@ -57,7 +57,7 @@ func (c *serviceClient) TraceDump(ctx context.Context, in *TraceDump) (RPCServic
 }
 
 type RPCService_TraceDumpClient interface {
-	Recv() (*TraceDetails, error)
+	Recv() (*TraceDetails, *TraceDumpReply, error)
 	api.Stream
 }
 
@@ -65,22 +65,25 @@ type serviceClient_TraceDumpClient struct {
 	api.Stream
 }
 
-func (c *serviceClient_TraceDumpClient) Recv() (*TraceDetails, error) {
+func (c *serviceClient_TraceDumpClient) Recv() (*TraceDetails, *TraceDumpReply, error) {
 	msg, err := c.Stream.RecvMsg()
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 	switch m := msg.(type) {
 	case *TraceDetails:
-		return m, nil
+		return m, nil, nil
 	case *TraceDumpReply:
+		if err := api.RetvalToVPPApiError(m.Retval); err != nil {
+			return nil, nil, err
+		}
 		err = c.Stream.Close()
 		if err != nil {
-			return nil, err
+			return nil, nil, err
 		}
-		return nil, io.EOF
+		return nil, m, io.EOF
 	default:
-		return nil, fmt.Errorf("unexpected message: %T %v", m, m)
+		return nil, nil, fmt.Errorf("unexpected message: %T %v", m, m)
 	}
 }
 
diff --git a/binapigen/gen_rpc.go b/binapigen/gen_rpc.go
index 33602ccc..0adadccb 100644
--- a/binapigen/gen_rpc.go
+++ b/binapigen/gen_rpc.go
@@ -134,7 +134,11 @@ func genService(g *GenFile, svc *Service) {
 			g.P("}")
 			g.P()
 			g.P("type ", streamApi, " interface {")
-			g.P("	Recv() (*", msgDetails.GoIdent, ", error)")
+			if msgReply != msgControlPingReply {
+				g.P("	Recv() (*", msgDetails.GoIdent, ", *", msgReply.GoIdent, ", error)")
+			} else {
+				g.P("	Recv() (*", msgDetails.GoIdent, ", error)")
+			}
 			g.P("	", govppApiPkg.Ident("Stream"))
 			g.P("}")
 			g.P()
@@ -144,18 +148,57 @@ func genService(g *GenFile, svc *Service) {
 			g.P("}")
 			g.P()
 
-			g.P("func (c *", streamImpl, ") Recv() (*", msgDetails.GoIdent, ", error) {")
+			if msgReply != msgControlPingReply {
+				g.P("func (c *", streamImpl, ") Recv() (*", msgDetails.GoIdent, ", *", msgReply.GoIdent, ", error) {")
+			} else {
+				g.P("func (c *", streamImpl, ") Recv() (*", msgDetails.GoIdent, ", error) {")
+			}
 			g.P("	msg, err := c.Stream.RecvMsg()")
-			g.P("	if err != nil { return nil, err }")
+			if msgReply != msgControlPingReply {
+				g.P("	if err != nil { return nil, nil, err }")
+			} else {
+				g.P("	if err != nil { return nil, err }")
+			}
 			g.P("	switch m := msg.(type) {")
 			g.P("	case *", msgDetails.GoIdent, ":")
-			g.P("		return m, nil")
+			if msgReply != msgControlPingReply {
+				g.P("		return m, nil, nil")
+			} else {
+				g.P("		return m, nil")
+			}
 			g.P("	case *", msgReply.GoIdent, ":")
+			if msgReply != msgControlPingReply {
+				if retvalField := getRetvalField(msgReply); retvalField != nil {
+					s := fmt.Sprint("(m.", retvalField.GoName, ")")
+					if fieldType := getFieldType(g, retvalField); fieldType != "int32" {
+						s = fmt.Sprint("(int32(m.", retvalField.GoName, "))")
+					}
+					g.P("if err := ", govppApiPkg.Ident("RetvalToVPPApiError"), s, "; err != nil {")
+					if msgReply != msgControlPingReply {
+						g.P("	return nil, nil, err")
+					} else {
+						g.P("	return nil, err")
+					}
+					g.P("}")
+				}
+			}
 			g.P("		err = c.Stream.Close()")
-			g.P("		if err != nil { return nil, err }")
-			g.P("		return nil, ", ioPkg.Ident("EOF"))
+			if msgReply != msgControlPingReply {
+				g.P("	if err != nil { return nil, nil, err }")
+			} else {
+				g.P("	if err != nil { return nil, err }")
+			}
+			if msgReply != msgControlPingReply {
+				g.P("		return nil, m, ", ioPkg.Ident("EOF"))
+			} else {
+				g.P("		return nil, ", ioPkg.Ident("EOF"))
+			}
 			g.P("	default:")
-			g.P("		return nil, ", fmtPkg.Ident("Errorf"), "(\"unexpected message: %T %v\", m, m)")
+			if msgReply != msgControlPingReply {
+				g.P("		return nil, nil, ", fmtPkg.Ident("Errorf"), "(\"unexpected message: %T %v\", m, m)")
+			} else {
+				g.P("		return nil, ", fmtPkg.Ident("Errorf"), "(\"unexpected message: %T %v\", m, m)")
+			}
 			g.P("}")
 		} else if rpc.MsgReply != nil {
 			g.P("out := new(", rpc.MsgReply.GoIdent, ")")