diff --git a/README.md b/README.md
index 95b4138072..c5fe405b54 100644
--- a/README.md
+++ b/README.md
@@ -359,7 +359,6 @@ type: ...
 uri/device/id: ...
 register:
   address: 40070
-  length: 2 # read length in words
   type: holding # holding or input
   decode: int32 # int16|32|64, uint16|32|64, float32|64 and u|int32s + float32s
 scale: -1 # floating point factor applied to result, e.g. for kW to W conversion
diff --git a/evcc.dist.yaml b/evcc.dist.yaml
index 4932271177..43d8f920a2 100644
--- a/evcc.dist.yaml
+++ b/evcc.dist.yaml
@@ -87,7 +87,6 @@ meters:
     id: 1
     register: # manual register configuration
       address: 40070
-      length: 2
       type: holding
       decode: int32
     scale: -1 # reverse direction
diff --git a/go.mod b/go.mod
index a7ad60552a..5a8cdd7528 100644
--- a/go.mod
+++ b/go.mod
@@ -34,7 +34,7 @@ require (
 	github.com/spf13/viper v1.6.3
 	github.com/tcnksm/go-latest v0.0.0-20170313132115-e3007ae9052e
 	github.com/technoweenie/multipartstreamer v1.0.1 // indirect
-	github.com/volkszaehler/mbmd v0.0.0-20200524120609-c683601720ed
+	github.com/volkszaehler/mbmd v0.0.0-20200524133250-a64175ed6a8a
 	golang.org/x/crypto v0.0.0-20200429183012-4b2356b1ed79 // indirect
 	golang.org/x/net v0.0.0-20200505041828-1ed23360d12c
 	golang.org/x/sys v0.0.0-20200501145240-bc7a7d42d5c3 // indirect
diff --git a/go.sum b/go.sum
index a547d8d6c0..64fc9009e4 100644
--- a/go.sum
+++ b/go.sum
@@ -251,8 +251,8 @@ github.com/technoweenie/multipartstreamer v1.0.1 h1:XRztA5MXiR1TIRHxH2uNxXxaIkKQ
 github.com/technoweenie/multipartstreamer v1.0.1/go.mod h1:jNVxdtShOxzAsukZwTSw6MDx5eUJoiEBsSvzDU9uzog=
 github.com/tmc/grpc-websocket-proxy v0.0.0-20190109142713-0ad062ec5ee5/go.mod h1:ncp9v5uamzpCO7NfCPTXjqaC+bZgJeR0sMTm6dMHP7U=
 github.com/ugorji/go v1.1.4/go.mod h1:uQMGLiO92mf5W77hV/PUCpI3pbzQx3CRekS0kk+RGrc=
-github.com/volkszaehler/mbmd v0.0.0-20200524120609-c683601720ed h1:oC2QZlpY+AbEPn/8TWvO4FiXrk9uHhCyT24b6wwa/JA=
-github.com/volkszaehler/mbmd v0.0.0-20200524120609-c683601720ed/go.mod h1:MmglPXoZJOT0r+tWwAjaaRWmuopdQOq2tWxbL9zvuxE=
+github.com/volkszaehler/mbmd v0.0.0-20200524133250-a64175ed6a8a h1:OURwSCpbOBMInNnNE7rmyDpvx/mK7CgZo2UhU6HDvRY=
+github.com/volkszaehler/mbmd v0.0.0-20200524133250-a64175ed6a8a/go.mod h1:MmglPXoZJOT0r+tWwAjaaRWmuopdQOq2tWxbL9zvuxE=
 github.com/xiang90/probing v0.0.0-20190116061207-43a291ad63a2/go.mod h1:UETIi67q53MR2AWcXfiuqkDkRtnGDLqkBTpCHuJHxtU=
 github.com/xordataexchange/crypt v0.0.3-0.20170626215501-b2862e3d0a77/go.mod h1:aYKd//L2LvnjZzWKhF00oedf4jCCReLcmhLdhm1A27Q=
 github.com/yuin/goldmark v1.1.27/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
diff --git a/provider/modbus.go b/provider/modbus.go
index 250a218655..14a4d39de3 100644
--- a/provider/modbus.go
+++ b/provider/modbus.go
@@ -46,6 +46,29 @@ func NewModbusFromConfig(log *util.Logger, typ string, other map[string]interfac
 	var device meters.Device
 	var op modbus.Operation
 
+	if cc.Value != "" && cc.Register.Decode != "" {
+		log.FATAL.Fatalf("config: modbus cannot have value and register both")
+	}
+
+	// model + value configured
+	if cc.Value != "" {
+		if err := modbus.ParseOperation(device, cc.Value, &op); err != nil {
+			log.FATAL.Fatalf("config: invalid value %s", cc.Value)
+		}
+
+		// if sunspec reading configured make sure model is defined or device won't be initalized
+		if op.SunSpec.Point != "" && cc.Model == "" {
+			cc.Model = "SunSpec"
+		}
+	}
+
+	// register configured
+	if cc.Register.Decode != "" {
+		if op.MBMD, err = modbus.RegisterOperation(cc.Register); err != nil {
+			log.TRACE.Fatal(err)
+		}
+	}
+
 	// model configured
 	if cc.Model != "" {
 		device, err = modbus.NewDevice(log, cc.Model, *cc.RTU)
@@ -65,20 +88,6 @@ func NewModbusFromConfig(log *util.Logger, typ string, other map[string]interfac
 		log.FATAL.Fatal(err)
 	}
 
-	// model + value configured
-	if cc.Value != "" {
-		if err := modbus.ParseOperation(device, cc.Value, &op); err != nil {
-			log.FATAL.Fatalf("invalid value %s", cc.Value)
-		}
-	}
-
-	// register configured
-	if cc.Register.Decode != "" {
-		if op.MBMD, err = modbus.RegisterOperation(cc.Register); err != nil {
-			log.TRACE.Fatal(err)
-		}
-	}
-
 	if cc.Scale == 0 {
 		cc.Scale = 1
 	}
diff --git a/util/modbus/modbus.go b/util/modbus/modbus.go
index 3d072e5aa0..f4af5ad5e9 100644
--- a/util/modbus/modbus.go
+++ b/util/modbus/modbus.go
@@ -195,8 +195,7 @@ type Operation struct {
 func ParseOperation(dev meters.Device, measurement string, op *Operation) (err error) {
 	// if measurement cannot be parsed it could be SunSpec model/block/point
 	if op.MBMD.IEC61850, err = meters.MeasurementString(measurement); err != nil {
-		opSunSpec := &SunSpecOperation{}
-		opSunSpec.Model, opSunSpec.Block, opSunSpec.Point, err = ParsePoint(measurement)
+		op.SunSpec.Model, op.SunSpec.Block, op.SunSpec.Point, err = ParsePoint(measurement)
 		return err
 	}