diff --git a/cmd/ghz/main.go b/cmd/ghz/main.go
index bf57029c..31e69356 100644
--- a/cmd/ghz/main.go
+++ b/cmd/ghz/main.go
@@ -2,6 +2,7 @@ package main
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io/ioutil"
 	"math"
@@ -11,10 +12,10 @@ import (
 	"strings"
 	"time"
 
+	"github.com/alecthomas/kingpin"
 	"github.com/bojand/ghz/printer"
 	"github.com/bojand/ghz/runner"
 	"github.com/jinzhu/configor"
-	"gopkg.in/alecthomas/kingpin.v2"
 )
 
 var (
@@ -25,49 +26,148 @@ var (
 
 	cPath = kingpin.Flag("config", "Path to the JSON or TOML config file that specifies all the test run settings.").PlaceHolder(" ").String()
 
-	proto    = kingpin.Flag("proto", `The Protocol Buffer .proto file.`).PlaceHolder(" ").String()
-	protoset = kingpin.Flag("protoset", "The compiled protoset file. Alternative to proto. -proto takes precedence.").PlaceHolder(" ").String()
-	call     = kingpin.Flag("call", `A fully-qualified method name in 'package.Service/method' or 'package.Service.Method' format.`).PlaceHolder(" ").String()
-	paths    = kingpin.Flag("import-paths", "Comma separated list of proto import paths. The current working directory and the directory of the protocol buffer file are automatically added to the import list.").Short('i').PlaceHolder(" ").String()
+	// Proto
+	isProtoSet = false
+	proto      = kingpin.Flag("proto", `The Protocol Buffer .proto file.`).
+			PlaceHolder(" ").IsSetByUser(&isProtoSet).String()
 
-	cacert     = kingpin.Flag("cacert", "File containing trusted root certificates for verifying the server.").PlaceHolder(" ").String()
-	cert       = kingpin.Flag("cert", "File containing client certificate (public key), to present to the server. Must also provide -key option.").PlaceHolder(" ").String()
-	key        = kingpin.Flag("key", "File containing client private key, to present to the server. Must also provide -cert option.").PlaceHolder(" ").String()
-	cname      = kingpin.Flag("cname", "Server name override when validating TLS certificate - useful for self signed certs.").PlaceHolder(" ").String()
-	skipVerify = kingpin.Flag("skipTLS", "Skip TLS client verification of the server's certificate chain and host name.").Default("false").Bool()
-	insecure   = kingpin.Flag("insecure", "Use plaintext and insecure connection.").Default("false").Bool()
-	authority  = kingpin.Flag("authority", "Value to be used as the :authority pseudo-header. Only works if -insecure is used.").PlaceHolder(" ").String()
+	isProtoSetSet = false
+	protoset      = kingpin.Flag("protoset", "The compiled protoset file. Alternative to proto. -proto takes precedence.").
+			PlaceHolder(" ").IsSetByUser(&isProtoSetSet).String()
 
-	c = kingpin.Flag("concurrency", "Number of requests to run concurrently. Total number of requests cannot be smaller than the concurrency level. Default is 50.").Short('c').Default("50").Uint()
-	n = kingpin.Flag("total", "Number of requests to run. Default is 200.").Short('n').Default("200").Uint()
-	q = kingpin.Flag("qps", "Rate limit, in queries per second (QPS). Default is no rate limit.").Default("0").Short('q').Uint()
-	t = kingpin.Flag("timeout", "Timeout for each request. Default is 20s, use 0 for infinite.").Default("20s").Short('t').Duration()
-	z = kingpin.Flag("duration", "Duration of application to send requests. When duration is reached, application stops and exits. If duration is specified, n is ignored. Examples: -z 10s -z 3m.").Short('z').Default("0").Duration()
-	x = kingpin.Flag("max-duration", "Maximum duration of application to send requests with n setting respected. If duration is reached before n requests are completed, application stops and exits. Examples: -x 10s -x 3m.").Short('x').Default("0").Duration()
+	isCallSet = false
+	call      = kingpin.Flag("call", `A fully-qualified method name in 'package.Service/method' or 'package.Service.Method' format.`).
+			PlaceHolder(" ").IsSetByUser(&isCallSet).String()
 
-	zstop = kingpin.Flag("duration-stop", "Specifies how duration stop is reported. Options are close, wait or ignore.").Default("close").String()
+	isImportSet = false
+	paths       = kingpin.Flag("import-paths", "Comma separated list of proto import paths. The current working directory and the directory of the protocol buffer file are automatically added to the import list.").
+			Short('i').PlaceHolder(" ").IsSetByUser(&isImportSet).String()
 
-	conns = kingpin.Flag("connections", "Number of connections to use. Concurrency is distributed evenly among all the connections. Default is 1.").Default("1").Uint()
+	// Security
+	isCACertSet = false
+	cacert      = kingpin.Flag("cacert", "File containing trusted root certificates for verifying the server.").
+			PlaceHolder(" ").IsSetByUser(&isCACertSet).String()
 
-	data     = kingpin.Flag("data", "The call data as stringified JSON. If the value is '@' then the request contents are read from stdin.").Short('d').PlaceHolder(" ").String()
-	dataPath = kingpin.Flag("data-file", "File path for call data JSON file. Examples: /home/user/file.json or ./file.json.").Short('D').PlaceHolder("PATH").PlaceHolder(" ").String()
-	binData  = kingpin.Flag("binary", "The call data comes as serialized binary message or multiple count-prefixed messages read from stdin.").Short('b').Default("false").Bool()
-	binPath  = kingpin.Flag("binary-file", "File path for the call data as serialized binary message or multiple count-prefixed messages.").Short('B').PlaceHolder(" ").String()
-	md       = kingpin.Flag("metadata", "Request metadata as stringified JSON.").Short('m').PlaceHolder(" ").String()
-	mdPath   = kingpin.Flag("metadata-file", "File path for call metadata JSON file. Examples: /home/user/metadata.json or ./metadata.json.").Short('M').PlaceHolder(" ").String()
-	si       = kingpin.Flag("stream-interval", "Interval for stream requests between message sends.").Default("0").Duration()
-	rmd      = kingpin.Flag("reflect-metadata", "Reflect metadata as stringified JSON used only for reflection request.").PlaceHolder(" ").String()
+	isCertSet = false
+	cert      = kingpin.Flag("cert", "File containing client certificate (public key), to present to the server. Must also provide -key option.").
+			PlaceHolder(" ").IsSetByUser(&isCertSet).String()
 
-	output = kingpin.Flag("output", "Output path. If none provided stdout is used.").Short('o').PlaceHolder(" ").String()
-	format = kingpin.Flag("format", "Output format. One of: summary, csv, json, pretty, html, influx-summary, influx-details. Default is summary.").Short('O').Default("summary").PlaceHolder(" ").Enum("summary", "csv", "json", "pretty", "html", "influx-summary", "influx-details")
+	isKeySet = false
+	key      = kingpin.Flag("key", "File containing client private key, to present to the server. Must also provide -cert option.").
+			PlaceHolder(" ").IsSetByUser(&isKeySet).String()
 
-	ct = kingpin.Flag("connect-timeout", "Connection timeout for the initial connection dial. Default is 10s.").Default("10s").Duration()
-	kt = kingpin.Flag("keepalive", "Keepalive time duration. Only used if present and above 0.").Default("0").Duration()
+	isCNameSet = false
+	cname      = kingpin.Flag("cname", "Server name override when validating TLS certificate - useful for self signed certs.").
+			PlaceHolder(" ").IsSetByUser(&isCNameSet).String()
+
+	isSkipSet  = false
+	skipVerify = kingpin.Flag("skipTLS", "Skip TLS client verification of the server's certificate chain and host name.").
+			Default("false").IsSetByUser(&isSkipSet).Bool()
+
+	isInsecSet = false
+	insecure   = kingpin.Flag("insecure", "Use plaintext and insecure connection.").
+			Default("false").IsSetByUser(&isInsecSet).Bool()
+
+	isAuthSet = false
+	authority = kingpin.Flag("authority", "Value to be used as the :authority pseudo-header. Only works if -insecure is used.").
+			PlaceHolder(" ").IsSetByUser(&isAuthSet).String()
+
+	// Run
+	isCSet = false
+	c      = kingpin.Flag("concurrency", "Number of requests to run concurrently. Total number of requests cannot be smaller than the concurrency level. Default is 50.").
+		Short('c').Default("50").IsSetByUser(&isCSet).Uint()
+
+	isNSet = false
+	n      = kingpin.Flag("total", "Number of requests to run. Default is 200.").
+		Short('n').Default("200").IsSetByUser(&isNSet).Uint()
+
+	isQSet = false
+	q      = kingpin.Flag("qps", "Rate limit, in queries per second (QPS). Default is no rate limit.").
+		Default("0").Short('q').IsSetByUser(&isQSet).Uint()
+
+	isTSet = false
+	t      = kingpin.Flag("timeout", "Timeout for each request. Default is 20s, use 0 for infinite.").
+		Default("20s").Short('t').IsSetByUser(&isTSet).Duration()
+
+	isZSet = false
+	z      = kingpin.Flag("duration", "Duration of application to send requests. When duration is reached, application stops and exits. If duration is specified, n is ignored. Examples: -z 10s -z 3m.").
+		Short('z').Default("0").IsSetByUser(&isZSet).Duration()
+
+	isXSet = false
+	x      = kingpin.Flag("max-duration", "Maximum duration of application to send requests with n setting respected. If duration is reached before n requests are completed, application stops and exits. Examples: -x 10s -x 3m.").
+		Short('x').Default("0").IsSetByUser(&isXSet).Duration()
+
+	isZStopSet = false
+	zstop      = kingpin.Flag("duration-stop", "Specifies how duration stop is reported. Options are close, wait or ignore.").
+			Default("close").IsSetByUser(&isZStopSet).String()
+
+	// Data
+	isDataSet = false
+	data      = kingpin.Flag("data", "The call data as stringified JSON. If the value is '@' then the request contents are read from stdin.").
+			Short('d').PlaceHolder(" ").IsSetByUser(&isDataSet).String()
+
+	isDataPathSet = false
+	dataPath      = kingpin.Flag("data-file", "File path for call data JSON file. Examples: /home/user/file.json or ./file.json.").
+			Short('D').PlaceHolder("PATH").PlaceHolder(" ").IsSetByUser(&isDataPathSet).String()
+
+	isBinDataSet = false
+	binData      = kingpin.Flag("binary", "The call data comes as serialized binary message or multiple count-prefixed messages read from stdin.").
+			Short('b').Default("false").IsSetByUser(&isBinDataSet).Bool()
+
+	isBinDataPathSet = false
+	binPath          = kingpin.Flag("binary-file", "File path for the call data as serialized binary message or multiple count-prefixed messages.").
+				Short('B').PlaceHolder(" ").IsSetByUser(&isBinDataPathSet).String()
+
+	isMDSet = false
+	md      = kingpin.Flag("metadata", "Request metadata as stringified JSON.").
+		Short('m').PlaceHolder(" ").IsSetByUser(&isMDSet).String()
+
+	isMDPathSet = false
+	mdPath      = kingpin.Flag("metadata-file", "File path for call metadata JSON file. Examples: /home/user/metadata.json or ./metadata.json.").
+			Short('M').PlaceHolder(" ").IsSetByUser(&isMDPathSet).String()
+
+	isSISet = false
+	si      = kingpin.Flag("stream-interval", "Interval for stream requests between message sends.").
+		Default("0").IsSetByUser(&isSISet).Duration()
+
+	isRMDSet = false
+	rmd      = kingpin.Flag("reflect-metadata", "Reflect metadata as stringified JSON used only for reflection request.").
+			PlaceHolder(" ").IsSetByUser(&isRMDSet).String()
+
+	// Output
+	isOutputSet = false
+	output      = kingpin.Flag("output", "Output path. If none provided stdout is used.").
+			Short('o').PlaceHolder(" ").IsSetByUser(&isOutputSet).String()
 
-	name = kingpin.Flag("name", "User specified name for the test.").PlaceHolder(" ").String()
-	tags = kingpin.Flag("tags", "JSON representation of user-defined string tags.").PlaceHolder(" ").String()
+	isFormatSet = false
+	format      = kingpin.Flag("format", "Output format. One of: summary, csv, json, pretty, html, influx-summary, influx-details. Default is summary.").
+			Short('O').Default("summary").PlaceHolder(" ").IsSetByUser(&isFormatSet).Enum("summary", "csv", "json", "pretty", "html", "influx-summary", "influx-details")
 
-	cpus = kingpin.Flag("cpus", "Number of cpu cores to use.").Default(strconv.FormatUint(uint64(nCPUs), 10)).Uint()
+	// Connection
+	isConnSet = false
+	conns     = kingpin.Flag("connections", "Number of connections to use. Concurrency is distributed evenly among all the connections. Default is 1.").
+			Default("1").IsSetByUser(&isConnSet).Uint()
+
+	isCTSet = false
+	ct      = kingpin.Flag("connect-timeout", "Connection timeout for the initial connection dial. Default is 10s.").
+		Default("10s").IsSetByUser(&isCTSet).Duration()
+
+	isKTSet = false
+	kt      = kingpin.Flag("keepalive", "Keepalive time duration. Only used if present and above 0.").
+		Default("0").IsSetByUser(&isKTSet).Duration()
+
+	// Meta
+	isNameSet = false
+	name      = kingpin.Flag("name", "User specified name for the test.").
+			PlaceHolder(" ").IsSetByUser(&isNameSet).String()
+
+	isTagsSet = false
+	tags      = kingpin.Flag("tags", "JSON representation of user-defined string tags.").
+			PlaceHolder(" ").IsSetByUser(&isTagsSet).String()
+
+	isCPUSet = false
+	cpus     = kingpin.Flag("cpus", "Number of cpu cores to use.").
+			Default(strconv.FormatUint(uint64(nCPUs), 10)).IsSetByUser(&isCPUSet).Uint()
 
 	host = kingpin.Arg("host", "Host and port to test.").String()
 )
@@ -80,18 +180,24 @@ func main() {
 
 	cfgPath := strings.TrimSpace(*cPath)
 
-	var cfg *config
+	var cfg config
 
 	if cfgPath != "" {
-		var conf config
-		err := configor.Load(&conf, cfgPath)
+		err := configor.Load(&cfg, cfgPath)
 		kingpin.FatalIfError(err, "")
 
-		cfg = &conf
+		args := os.Args[1:]
+		if len(args) > 1 {
+			var cmdCfg config
+			err = createConfigFromArgs(&cmdCfg)
+			kingpin.FatalIfError(err, "")
+
+			err = mergeConfig(&cfg, &cmdCfg)
+			kingpin.FatalIfError(err, "")
+		}
 	} else {
+		err := createConfigFromArgs(&cfg)
 
-		var err error
-		cfg, err = createConfigFromArgs()
 		kingpin.FatalIfError(err, "")
 	}
 
@@ -189,7 +295,11 @@ func handleError(err error) {
 	}
 }
 
-func createConfigFromArgs() (*config, error) {
+func createConfigFromArgs(cfg *config) error {
+	if cfg == nil {
+		return errors.New("config cannot be nil")
+	}
+
 	iPaths := []string{}
 	pathsTrimmed := strings.TrimSpace(*paths)
 	if pathsTrimmed != "" {
@@ -200,7 +310,7 @@ func createConfigFromArgs() (*config, error) {
 	if *binData {
 		b, err := ioutil.ReadAll(os.Stdin)
 		if err != nil {
-			return nil, err
+			return err
 		}
 
 		binaryData = b
@@ -210,14 +320,14 @@ func createConfigFromArgs() (*config, error) {
 	*md = strings.TrimSpace(*md)
 	if *md != "" {
 		if err := json.Unmarshal([]byte(*md), &metadata); err != nil {
-			return nil, fmt.Errorf("Error unmarshaling metadata '%v': %v", *md, err.Error())
+			return fmt.Errorf("Error unmarshaling metadata '%v': %v", *md, err.Error())
 		}
 	}
 
 	var dataObj interface{}
 	if *data != "@" && strings.TrimSpace(*data) != "" {
 		if err := json.Unmarshal([]byte(*data), &dataObj); err != nil {
-			return nil, fmt.Errorf("Error unmarshaling data '%v': %v", *data, err.Error())
+			return fmt.Errorf("Error unmarshaling data '%v': %v", *data, err.Error())
 		}
 	}
 
@@ -225,7 +335,7 @@ func createConfigFromArgs() (*config, error) {
 	*tags = strings.TrimSpace(*tags)
 	if *tags != "" {
 		if err := json.Unmarshal([]byte(*tags), &tagsMap); err != nil {
-			return nil, fmt.Errorf("Error unmarshaling tags '%v': %v", *tags, err.Error())
+			return fmt.Errorf("Error unmarshaling tags '%v': %v", *tags, err.Error())
 		}
 	}
 
@@ -233,47 +343,189 @@ func createConfigFromArgs() (*config, error) {
 	*rmd = strings.TrimSpace(*rmd)
 	if *rmd != "" {
 		if err := json.Unmarshal([]byte(*rmd), &rmdMap); err != nil {
-			return nil, fmt.Errorf("Error unmarshaling reflection metadata '%v': %v", *rmd, err.Error())
+			return fmt.Errorf("Error unmarshaling reflection metadata '%v': %v", *rmd, err.Error())
 		}
 	}
 
-	cfg := &config{
-		Host:            *host,
-		Proto:           *proto,
-		Protoset:        *protoset,
-		Call:            *call,
-		RootCert:        *cacert,
-		Cert:            *cert,
-		Key:             *key,
-		SkipTLSVerify:   *skipVerify,
-		Insecure:        *insecure,
-		Authority:       *authority,
-		CName:           *cname,
-		N:               *n,
-		C:               *c,
-		Connections:     *conns,
-		QPS:             *q,
-		Z:               Duration(*z),
-		X:               Duration(*x),
-		Timeout:         Duration(*t),
-		ZStop:           *zstop,
-		Data:            dataObj,
-		DataPath:        *dataPath,
-		BinData:         binaryData,
-		BinDataPath:     *binPath,
-		Metadata:        &metadata,
-		MetadataPath:    *mdPath,
-		SI:              Duration(*si),
-		Output:          *output,
-		Format:          *format,
-		ImportPaths:     iPaths,
-		DialTimeout:     Duration(*ct),
-		KeepaliveTime:   Duration(*kt),
-		CPUs:            *cpus,
-		Name:            *name,
-		Tags:            &tagsMap,
-		ReflectMetadata: &rmdMap,
-	}
-
-	return cfg, nil
+	cfg.Host = *host
+	cfg.Proto = *proto
+	cfg.Protoset = *protoset
+	cfg.Call = *call
+	cfg.RootCert = *cacert
+	cfg.Cert = *cert
+	cfg.Key = *key
+	cfg.SkipTLSVerify = *skipVerify
+	cfg.Insecure = *insecure
+	cfg.Authority = *authority
+	cfg.CName = *cname
+	cfg.N = *n
+	cfg.C = *c
+	cfg.QPS = *q
+	cfg.Z = Duration(*z)
+	cfg.X = Duration(*x)
+	cfg.Timeout = Duration(*t)
+	cfg.ZStop = *zstop
+	cfg.Data = dataObj
+	cfg.DataPath = *dataPath
+	cfg.BinData = binaryData
+	cfg.BinDataPath = *binPath
+	cfg.Metadata = &metadata
+	cfg.MetadataPath = *mdPath
+	cfg.SI = Duration(*si)
+	cfg.Output = *output
+	cfg.Format = *format
+	cfg.ImportPaths = iPaths
+	cfg.Connections = *conns
+	cfg.DialTimeout = Duration(*ct)
+	cfg.KeepaliveTime = Duration(*kt)
+	cfg.CPUs = *cpus
+	cfg.Name = *name
+	cfg.Tags = &tagsMap
+	cfg.ReflectMetadata = &rmdMap
+
+	return nil
+}
+
+func mergeConfig(dest *config, src *config) error {
+	if src == nil || dest == nil {
+		return errors.New("config cannot be nil")
+	}
+
+	if isProtoSet {
+		dest.Proto = src.Proto
+	}
+
+	if isProtoSetSet {
+		dest.Protoset = src.Protoset
+	}
+
+	if isCallSet {
+		dest.Call = src.Call
+	}
+
+	if isCACertSet {
+		dest.RootCert = src.RootCert
+	}
+
+	if isCertSet {
+		dest.Cert = src.Cert
+	}
+
+	if isKeySet {
+		dest.Key = src.Key
+	}
+
+	if isSkipSet {
+		dest.SkipTLSVerify = src.SkipTLSVerify
+	}
+
+	if isInsecSet {
+		dest.Insecure = src.Insecure
+	}
+
+	if isAuthSet {
+		dest.Authority = src.Authority
+	}
+
+	if isCNameSet {
+		dest.CName = src.CName
+	}
+
+	if isNSet {
+		dest.N = src.N
+	}
+
+	if isCSet {
+		dest.C = src.C
+	}
+
+	if isQSet {
+		dest.QPS = src.QPS
+	}
+
+	if isZSet {
+		dest.Z = src.Z
+	}
+
+	if isXSet {
+		dest.X = src.X
+	}
+
+	if isTSet {
+		dest.Timeout = src.Timeout
+	}
+
+	if isZStopSet {
+		dest.ZStop = src.ZStop
+	}
+
+	if isDataSet {
+		dest.Data = src.Data
+	}
+
+	if isDataPathSet {
+		dest.DataPath = src.DataPath
+	}
+
+	if isBinDataSet {
+		dest.BinData = src.BinData
+	}
+
+	if isBinDataPathSet {
+		dest.BinDataPath = src.BinDataPath
+	}
+
+	if isMDSet {
+		dest.Metadata = src.Metadata
+	}
+
+	if isMDPathSet {
+		dest.MetadataPath = src.MetadataPath
+	}
+
+	if isSISet {
+		dest.SI = src.SI
+	}
+
+	if isOutputSet {
+		dest.Output = src.Output
+	}
+
+	if isFormatSet {
+		dest.Format = src.Format
+	}
+
+	if isImportSet {
+		dest.ImportPaths = src.ImportPaths
+	}
+
+	if isConnSet {
+		dest.Connections = src.Connections
+	}
+
+	if isCTSet {
+		dest.DialTimeout = src.DialTimeout
+	}
+
+	if isKTSet {
+		dest.KeepaliveTime = src.KeepaliveTime
+	}
+
+	if isCPUSet {
+		dest.CPUs = src.CPUs
+	}
+
+	if isNameSet {
+		dest.Name = src.Name
+	}
+
+	if isTagsSet {
+		dest.Tags = src.Tags
+	}
+
+	if isRMDSet {
+		dest.ReflectMetadata = src.ReflectMetadata
+	}
+
+	return nil
 }
diff --git a/go.mod b/go.mod
index 5fc3f26c..90750fe8 100644
--- a/go.mod
+++ b/go.mod
@@ -3,6 +3,7 @@ module github.com/bojand/ghz
 go 1.13
 
 require (
+	github.com/alecthomas/kingpin v1.3.8-0.20191105203113-8c96d1c22481
 	github.com/alecthomas/template v0.0.0-20190718012654-fb15b899a751
 	github.com/bojand/hri v1.1.0
 	github.com/dgrijalva/jwt-go v3.2.0+incompatible // indirect
@@ -26,6 +27,5 @@ require (
 	go.uber.org/multierr v1.2.0
 	golang.org/x/net v0.0.0-20191021144547-ec77196f6094
 	google.golang.org/grpc v1.24.0
-	gopkg.in/alecthomas/kingpin.v2 v2.2.6
 	gopkg.in/go-playground/assert.v1 v1.2.1 // indirect
 )
diff --git a/go.sum b/go.sum
index a38c3571..f4322c8e 100644
--- a/go.sum
+++ b/go.sum
@@ -6,6 +6,8 @@ github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
 github.com/Shopify/sarama v1.19.0/go.mod h1:FVkBWblsNy7DGZRfXLU0O9RCGt5g3g3yEuWXgklEdEo=
 github.com/Shopify/toxiproxy v2.1.4+incompatible/go.mod h1:OXgGpZ6Cli1/URJOF1DMxUHB2q5Ap20/P/eIdh4G0pI=
+github.com/alecthomas/kingpin v1.3.8-0.20191105203113-8c96d1c22481 h1:NXM4vkjHeFp3bbp0z/u0AdQRLg6b5LrPeFwgjVHUW58=
+github.com/alecthomas/kingpin v1.3.8-0.20191105203113-8c96d1c22481/go.mod h1:b6br6/pDFSfMkBgC96TbpOji05q5pa+v5rIlS0Y6XtI=
 github.com/alecthomas/template v0.0.0-20160405071501-a0175ee3bccc/go.mod h1:LOuyumcjzFXgccqObfd/Ljyb9UuFJ6TxHnclSeseNhc=
 github.com/alecthomas/template v0.0.0-20190718012654-fb15b899a751 h1:JYp7IbQjafoB+tBA3gMyHYHrpOtNuDiK/uB5uXxq5wM=
 github.com/alecthomas/template v0.0.0-20190718012654-fb15b899a751/go.mod h1:LOuyumcjzFXgccqObfd/Ljyb9UuFJ6TxHnclSeseNhc=
diff --git a/www/docs/examples.md b/www/docs/examples.md
index 9dc9b9e7..d044d2fc 100644
--- a/www/docs/examples.md
+++ b/www/docs/examples.md
@@ -119,11 +119,17 @@ Note that only one of `-proto` or `-protoset` options will be used. `-proto` tak
 Alternatively `ghz` can be used with [Prototool](https://github.com/uber/prototool) using the [`descriptor-set`](https://github.com/uber/prototool/tree/dev/docs#prototool-descriptor-set) command:
 
 ```
-ghz -protoset $(prototool descriptor-set --include-imports --tmp) ...
+ghz --protoset $(prototool descriptor-set --include-imports --tmp) ...
 ```
 
 Finally we can specify all settings, including the target host, conveniently in a JSON or TOML config file.
 
 ```sh
-ghz -config ./config.json
+ghz --config ./config.json
+```
+
+Config file settings can be combined with command line arguments. CLI options overwrite config file options.
+
+```sh
+ghz --config ./config.json -c 20 -n 1000
 ```
diff --git a/www/docs/options.md b/www/docs/options.md
index 5dcbef2e..c703ed0c 100644
--- a/www/docs/options.md
+++ b/www/docs/options.md
@@ -58,6 +58,12 @@ Value to be used as the `:authority` pseudo-header. Only works if `-insecure` is
 
 Path to the JSON or TOML [config file](example_config.md) that specifies all the test settings.
 
+Config file settings can be combined with command line arguments. CLI options overwrite config file options.
+
+```sh
+ghz --config=./config.json -c 20 -n 1000
+```
+
 ### `-c`, `--concurrency`
 
 Number of requests to run concurrently. Total number of requests cannot be smaller than the concurrency level. Default is `50`. For example to do requests in series without any concurrency set to `1`. `ghz` takes the `concurrency` argument and spawns that many worker goroutines. By default all goroutine workers share a single connection.