diff --git a/adc/conn.go b/adc/conn.go
index efc4cd1..5f549fa 100644
--- a/adc/conn.go
+++ b/adc/conn.go
@@ -143,8 +143,8 @@ func (c *Conn) SetWriteTimeout(dt time.Duration) {
 	}
 }
 
-func (c *Conn) ZOn() error {
-	return c.w.EnableZlib()
+func (c *Conn) ZOn(lvl int) error {
+	return c.w.EnableZlibLevel(lvl)
 }
 
 // Close closes the connection.
diff --git a/hub/cmds.go b/hub/cmds.go
index 4afed85..2f9d689 100644
--- a/hub/cmds.go
+++ b/hub/cmds.go
@@ -548,7 +548,7 @@ func cmdParseString(text string) (string, string, error) {
 	if len(text) == 0 {
 		return "", text, errCmdInvalidArg
 	}
-	if text[0] != '"' && text[1] != '`' {
+	if text[0] != '"' && text[0] != '`' {
 		// unquoted string
 		i := strings.IndexByte(text, ' ')
 		if i < 0 {
diff --git a/hub/config.go b/hub/config.go
index c69836b..3d6b955 100644
--- a/hub/config.go
+++ b/hub/config.go
@@ -16,6 +16,10 @@ const (
 	ConfigHubMOTD    = "hub.motd"
 )
 
+const (
+	ConfigZlibLevel = "zlib.level"
+)
+
 var configAliases = map[string]string{
 	"name":    ConfigHubName,
 	"desc":    ConfigHubDesc,
@@ -132,6 +136,7 @@ func (h *Hub) ConfigKeys() []string {
 		ConfigHubOwner,
 		ConfigHubWebsite,
 		ConfigHubEmail,
+		ConfigZlibLevel,
 	}
 	h.conf.RLock()
 	for k := range h.conf.m {
@@ -162,6 +167,12 @@ func (h *Hub) GetConfig(key string) (interface{}, bool) {
 			return nil, false
 		}
 		return v, true
+	case ConfigZlibLevel:
+		v, ok := h.GetConfigInt(key)
+		if !ok {
+			return nil, false
+		}
+		return v, true
 	}
 	h.conf.RLock()
 	v, ok := h.conf.m[key]
@@ -309,6 +320,8 @@ func (h *Hub) setConfigInt(key string, val int64) {
 		return
 	}
 	switch key {
+	case ConfigZlibLevel:
+		h.setZlibLevel(int(val))
 	default:
 		h.setConfigMap(key, val)
 	}
@@ -324,6 +337,8 @@ func (h *Hub) GetConfigInt(key string) (int64, bool) {
 		key = alias
 	}
 	switch key {
+	case ConfigZlibLevel:
+		return int64(h.zlibLevel()), true
 	default:
 		v, ok := h.getConfigMap(key)
 		if !ok || v == nil {
diff --git a/hub/hub.go b/hub/hub.go
index 7973f2f..5bf20db 100644
--- a/hub/hub.go
+++ b/hub/hub.go
@@ -66,6 +66,7 @@ func NewHub(conf Config) (*Hub, error) {
 		tls:     conf.TLS,
 	}
 	h.conf.Config = conf
+	h.setZlibLevel(-1)
 	if conf.FallbackEncoding != "" {
 		enc, err := htmlindex.Get(conf.FallbackEncoding)
 		if err != nil {
@@ -145,6 +146,9 @@ type Hub struct {
 		names  map[string]struct{} // no aliases
 		byName map[string]*Command
 	}
+	zlib struct {
+		level int32
+	}
 
 	globalChat *Room
 	rooms      rooms
@@ -172,6 +176,20 @@ func (h *Hub) decShare(v uint64) {
 	cntShare.Add(-float64(v))
 }
 
+func (h *Hub) zlibLevel() int {
+	return int(atomic.LoadInt32(&h.zlib.level))
+}
+
+func (h *Hub) setZlibLevel(level int) {
+	if level < -1 {
+		level = -1
+	}
+	if level > 9 {
+		level = 9
+	}
+	atomic.StoreInt32(&h.zlib.level, int32(level))
+}
+
 type Stats struct {
 	Name     string      `json:"name"`
 	Desc     string      `json:"desc,omitempty"`
diff --git a/hub/hub_adc.go b/hub/hub_adc.go
index 2ef45bd..89b4f67 100644
--- a/hub/hub_adc.go
+++ b/hub/hub_adc.go
@@ -221,12 +221,12 @@ func (h *Hub) adcStageProtocol(c *adc.Conn, cinfo *ConnInfo) (*adcPeer, error) {
 		return nil, fmt.Errorf("client does not support TIGR")
 	}
 
-	if mutual.IsSet(adc.FeaZLIF) {
+	if lvl := h.zlibLevel(); lvl != 0 && mutual.IsSet(adc.FeaZLIF) {
 		err = c.WriteInfoMsg(adc.ZOn{})
 		if err != nil {
 			return nil, err
 		}
-		err = c.ZOn()
+		err = c.ZOn(lvl)
 		if err != nil {
 			return nil, err
 		}
diff --git a/hub/hub_nmdc.go b/hub/hub_nmdc.go
index 7a5d565..e57dec0 100644
--- a/hub/hub_nmdc.go
+++ b/hub/hub_nmdc.go
@@ -333,8 +333,8 @@ func (h *Hub) nmdcAccept(peer *nmdcPeer) error {
 	if err != nil {
 		return err
 	}
-	if peer.fea.Has(nmdcp.ExtZPipe0) {
-		err = c.ZOn() // flushes
+	if lvl := h.zlibLevel(); lvl != 0 && peer.fea.Has(nmdcp.ExtZPipe0) {
+		err = c.ZOn(lvl) // flushes
 	} else {
 		err = c.Flush()
 	}
diff --git a/hub/plugins/tor/go.sum b/hub/plugins/tor/go.sum
index 53ca9da..0f6d06e 100644
--- a/hub/plugins/tor/go.sum
+++ b/hub/plugins/tor/go.sum
@@ -83,6 +83,7 @@ github.com/direct-connect/go-dc v0.7.2/go.mod h1:AwUTf54jhNPJvs+QNHoZxEb3p0LS8ik
 github.com/direct-connect/go-dc v0.7.3/go.mod h1:AwUTf54jhNPJvs+QNHoZxEb3p0LS8ik+2t0R8b4+MdI=
 github.com/direct-connect/go-dc v0.7.4/go.mod h1:AwUTf54jhNPJvs+QNHoZxEb3p0LS8ik+2t0R8b4+MdI=
 github.com/direct-connect/go-dc v0.8.0/go.mod h1:AwUTf54jhNPJvs+QNHoZxEb3p0LS8ik+2t0R8b4+MdI=
+github.com/direct-connect/go-dc v0.8.1 h1:PSE7WRV+XU+CHkis1RPo73Jnky/Kzn1JZipsGyQm3Dg=
 github.com/direct-connect/go-dc v0.8.1/go.mod h1:AwUTf54jhNPJvs+QNHoZxEb3p0LS8ik+2t0R8b4+MdI=
 github.com/docker/go-connections v0.4.0/go.mod h1:Gbd7IOopHjR8Iph03tsViu4nIes5XhDvyHbTtUxmeec=
 github.com/docker/go-units v0.3.3/go.mod h1:fgPhTUdO+D/Jk86RDLlptpiXQzgHJF7gydDDbaIK4Dk=
@@ -307,6 +308,7 @@ golang.org/x/crypto v0.0.0-20190404164418-38d8ce5564a5/go.mod h1:WFFai1msRO1wXaE
 golang.org/x/crypto v0.0.0-20190418165655-df01cb2cc480 h1:O5YqonU5IWby+w98jVUG9h7zlCWCcH4RHyPVReBmhzk=
 golang.org/x/crypto v0.0.0-20190418165655-df01cb2cc480/go.mod h1:WFFai1msRO1wXaEeE5yQxYXgSfI8pQAWXbQop6sCtWE=
 golang.org/x/crypto v0.0.0-20190424203555-c05e17bb3b2d/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
+golang.org/x/crypto v0.0.0-20190426145343-a29dc8fdc734 h1:p/H982KKEjUnLJkM3tt/LemDnOc1GiZL5FCVlORJ5zo=
 golang.org/x/crypto v0.0.0-20190426145343-a29dc8fdc734/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/exp v0.0.0-20190121172915-509febef88a4/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
 golang.org/x/exp v0.0.0-20190306152737-a1d7652674e8/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
@@ -341,6 +343,7 @@ golang.org/x/net v0.0.0-20190420063019-afa5a82059c6/go.mod h1:t9HGtf8HONx5eT2rtn
 golang.org/x/net v0.0.0-20190424112056-4829fb13d2c6/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20190501004415-9ce7a6920f09/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20190502183928-7f726cade0ab/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/net v0.0.0-20190503192946-f4e77d36d62c h1:uOCk1iQW6Vc18bnC13MfzScl+wdKBmM9Y9kU7Z83/lw=
 golang.org/x/net v0.0.0-20190503192946-f4e77d36d62c/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
 golang.org/x/oauth2 v0.0.0-20181017192945-9dcd33a902f4/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
@@ -376,6 +379,7 @@ golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.1-0.20180807135948-17ff2d5776d2 h1:z99zHgr7hKfrUcX/KsoJk5FJfjTceCKIp96+biqP4To=
 golang.org/x/text v0.3.1-0.20180807135948-17ff2d5776d2/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.1/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
+golang.org/x/text v0.3.2 h1:tW2bmiBqwgJj/UpqtC8EpXEZVYOwU0yG4iWbprSVAcs=
 golang.org/x/text v0.3.2/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
 golang.org/x/time v0.0.0-20180412165947-fbb02b2291d2/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
 golang.org/x/time v0.0.0-20181108054448-85acf8d2951c/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
diff --git a/nmdc/conn.go b/nmdc/conn.go
index 1e53fa6..1420579 100644
--- a/nmdc/conn.go
+++ b/nmdc/conn.go
@@ -204,8 +204,8 @@ func (c *Conn) SetFallbackEncoding(enc encoding.Encoding) {
 	c.fallback = enc
 }
 
-func (c *Conn) ZOn() error {
-	return c.w.ZOn()
+func (c *Conn) ZOn(lvl int) error {
+	return c.w.ZOnLevel(lvl)
 }
 
 // Close closes the connection.